How often do I need to rest my body?

Resting will not make you lose all of your progress. I wouldn't slow down but maybe find a good workout split, try finding a 4 or 5 day split from BodyBuilding.com. Basically you work out 4 or 5 days with planned rest days.

A typical 5 day split looks like this:

Day 1: Legs/Abs
Day 2: Chest
Day 3: Back/Abs*
Day 4: Rest
Day 5: Shoulder/Abs*
Day 6: Arms
Day 7: Rest

When you get more serious into it (if you ever do) every month & a half you can "deload" which is where you do the same workouts with lighter weight / less reps that way you're still actively working your muscles but it gives them time to repair & get ready to load more weight on the bar.

You can also take an active rest day where you go out hiking, walking, swimming, something physical but not intense exercise.

Congrats on 26lbs in 2 months.

you had a question of "am i doing too much", i would think your body is saying yes at the moment. maybe take a few days off and reduce the schedule a bit and see how that works for you.

once a quarter i take a week off, completely from all exercise. over the years 25+ i have found that my body grows and recovers better if it gets a needed break once in a while. and the week off has never caused me to "lose" anything significant but allows both the body and the mind to recover and rejuvenate. as posted in earlier response, let your body tell you when its ready to return.

50 pounds ago, i used to lift 5 days a week (for a long time prior also) and play on 3 softball teams. Your body will tell you when you need rest. I know it sounds over simplified, but its true. As you have probably been able to tell during your weight loss, our bodies are pretty freaking amazing at telling us what we are doing, as to if its wrong or right. I am now doing cardio everyday but sunday (30-40 mins) and light circuit lifting 3 times a week for like 20 minutes. I wold say if you are sore, or abnormally tired, take the day off, or do a quick 10 minute stretch or core workout, or, just go for a walk!

Age is a factor as well; how old are you?

The following applies to myself and my wife:

http://www.bodybuilding.com/fun/sisco14.htm

Couple of things going on to consider...

1 - age...I'm pushing 40 and I don't recover as readily as I did in my 20s...to boot, nutrient timing and quality are more important to my recovery now than they ever were when I was younger. I always take at least 1 but usually 2 "active" rest days per week. I say "active" because I still do walking and do some yoga or play golf or whatever with the boys. I'm just not out there training and pushing and otherwise vigorously exerting myself.

2 - You said you want to bulk...bulking is going to require some intense sessions in the weight room followed by quite a bit of rest. Rest is where that magic happens. Most people I know who do a true bulk, a) eat, eat, eat; b) hit the weight room hard a good 4x weekly with a solid hypertrophy program; and c) don't do much in the way of cardiovascular training while they are bulking.

Most people I know who do this will at most, do some walking or really lite work on the stair stepper or just do some recreational kind of stuff...they don't actively train their cardiovascular systems during their bulk. The reason being that for one thing, it requires you to eat even more...and in a bulk you're already eating quite a bit and that can be difficult to do day in and day out. Secondly, intense cardio training is going to interfere with your rest and thus your gains.