Peachy is right, shin splints have a plethora of causes, but one of the most common is wearing the wrong shoes, with overuse being right behind. I started a few weeks ago in a pair of 15 year old sneakers. They saw a lot of use, and then none, and then a lot, and then none (thusly, my needing to lose 80+ lbs when I started losing weight!) They were just too old. They felt comfy to me, but they were cross-trainers, not running shoes. After a week of rain and not getting outside, I got fitted for running shoes at a running store in NJ. Great folks there. The gentleman who worked with me first measured my feet to make sure I'd be in the right size, and then looked at my arches. He then had me walk for a little bit for him in my barefeet, watching as I walked away from and towards him. He paid attention to how my foot strikes the ground, basically did I pronate in one direction or the other (letting the foot hit the ground on one side or the other heavily). He then brought out 3 different pairs of shoes for me to try on based on all of that, and had me walk around the store in each, stretch, jog, whatever. I ended up picking the first pair (which is apparently pretty common) but I walked around with one foot in them, and one foot in the last one for a few minutes before deciding, just paying attention to how they felt, and not which was on which foot. This experience taught me what being actually fitted for a shoe was like! It was nifty. Now, I'm back on the road, and I've had zero shin splints. The shoes are lighter than my ancient ones, feel wonderful, and are light as all get out.

Overuse, well...you're new to this! Go a little gentle on yourself. 3 days a week is not meant to be 3 days in a row. Give yourself a day off in between. Walk, bike, do strength training, dance, do something on the other days, but give your running muscles a little bit of a rest. 3 days of exercise is good for somebody who isn't looking to get into shape, but to maintain, most of us are looking to lose, or maintain weight and get into awesome shape!

Stretching also plays a role. Shin splints can come from not stretching out your calf muscles enough. There are all sorts of recommendations for stretches, but before and after I step off my front porch I first do these like...wall pushup things. I stand with my hands up on a wall, and then lean forward, like doing a pushup. I hold this for a little bit, and then move one foot up to the wall, and the the other. I stretch my quads my grabbing my foot behind me and pulling it up to my butt. Then I stand on the edge of the step and stretch my toes down, and then back up. Afterwards at my desk, if my shins are feeling a little tight, I'll trace the alphabet in the air with my toes. That's just what I do, there are all sorts of sights with information about stretching!

I was fitted for running shoes yesterday at Fleet Feet. The people there were really nice and helpful. The fitting didn't cost anything. I ended up spending $110 on a pair of shoes that are perfect for me. This morning, I took them on a test run and noticed that I had more stamina (I'm on week 4 day 2 of c25k) and that they helped me have better running form. Before, I used to have a lot of trouble with shin pain. I think the problem is solved.

My recommendation for you: save up to get yourself a pair of shoes that are right for your feet, gait, stride... it's better than spending lots of money on doctors bills later (and that's sure to add up to more than $110). Until then, walk instead?