Gaining weight, is it purely about the number of kcals?

I already take whey protein. If I want to bulk what kind of supplement I have to take? high in carbs and protein? or low in carbs and high in protein? I find very hard to have massive meals, so that's why I consider to eat or drink every three hours.

I also started thinking about my training program, I think i am doing too much cardio at the moment (5 sessions per week), maybe replace 3 sessions of cardio by weight lifting. For my weight lifting session, should i do heavy or light?

So the cardio isn't for some race or event or test or something?
I thought it kinda needed to be done, at the expense of putting on muscle right now hence the reason to wait until winter.

If you aren't training for something specific, you are dead on correct, massive cardio will impact ability to put on muscle from lifting, as it'll tend to destroy muscle mass depending on how much you do.

If you can do the lifting now, for goodness sake do it now. Why put it off. Well, unless you are a member of Procrastinator's Anonymous, in which case you have to put off today what could be done tomorrow.

The only way to tell your body you want more muscle, is to overload it with weight. If you overload it with reps and light weight you are telling it you want more endurance, which is more glucose stores, not more muscle. If just light weight, you aren't asking it to do anything.
And make the cardio on between days easy going, as you don't want to tire out muscle you will use the next day or you won't be able to overload them with weight, nor do you want to kill the recovery and repair from the prior day's workout.

You don't need supplements until you are experienced after several years and it's difficult to get any kind of improvements, they really won't make a difference right now where what you eat and how you lift has a much bigger effect on making improvements.

Get your protein to 0.82 grams per lb of body weight, fat to 0.35, and carbs is the rest.
In MFP, lower the protein % until the fat is right, and then lower the carb % until the protein is right.

Hey, I was wearing hoodie to hide how skinny I was. Even if I was eating a lot and going to gym nothing seems to work. My breakthrough moment came when one girl told me that it isn´t attractive and I decided to really do something with it and start working on myself hard.

Different things work for different people and I was lucky enough to find one that worked for me. I gained 8 lbs in one month and it's been a life changer. I'm a little embarrased to post my before and after photos here but if anyone actually cares to hear what I've been doing then I'd be happy to help in any way.

Thanks heybales for your response. I am going to follow the Strong lift 5x5 training program from today (after my race). I will try to do it with the maximum of weight I can lift. I also think it's never good to totally give up on cardio, so I will probably try to add one or two session of cardio.

Well, make sure you read the program, don't just jump in and do the lifts as heavy as you can. It's very specific as to starting for a reason.

And true on cardio, in fact great time for a heavy cardio workout like intervals or such is right after the lifting, part of the workout. True your performance will be impacted once you get up to heavier weights, but it's exactly the kind of training that benefits a race, running tired. So you are training for the end of race.

I just broke my rower. It maybe a sign I have to do less cardio and do more weight lifting. This morning I run the 10k in 35 minutes and 36 seconds. Not too bad I think.

I started to read the program. Correct me if I am wrong but there is no exercise to work out the biceps. Is that correct? So basically if I want to bulk muscle I need to lift heavy weight, is that correct?

Great pace, strength can help that for sure, but not much because that's good already.

The bent over row works the bicep, and since you get up to some heavy weight for the back to get a workout, your bicep really gets one.
If you like, you can throw in some chin-ups at the end of one of the days, palms back, and work the back and biceps some more big time.

Also, the weight gain is all about the diet. The thing is I never know if I eat enough food for that (I dont really count the number of kcal).

Today I had one pot of peanut butter, two toast, one cookie, 2-3 latte, one eggs cress baguette. I am going to train now. This evening I am planning to have a can of tuna with some vegs and dressing. For the desert, probably some ice cream with a mug of milk. For me this is a big amount of food, do I need to eat that every day to gain weight? or should I just reduce cardio?

I am trying to eat high protein food (peanut butter, milk and eggs) and stay away from the ****ty food (e.g. cookies)

You'll probably need to log for for a couple weeks to get an idea of where a number is, just so you know how much you have to go up.

And if ever the level of food seems high, or expensive for amount of protein trying to obtain, then indeed, less cardio will mean needing to eat less.

You can keep cardio gains with a few well placed cardio workouts. Once weekly slower paced run to keep the lower fat-burning aerobic system in shape, and once weekly interval session to keep the higher carb-burning system in shape. Anything else would be about improving, or just getting the feet used to total time on them for a race.
But at your level of pace, to see increased performance would require doing a bunch more very specific training, but those 2 work outs would at least keep your gains.