I have always had irregular menstrual cycles. I'm 19, and about 300 pounds. But I skipped a month, then had a three week period. Then it went away. Then after a week it came back and now it's on its second week. Is it stress? I don't have sex at all.

As for blood clots, They're the main problem. They are constant, and so I find myself going to the restroom a lot before the sensation is disgusting. What could it be? I don't exercise, so maybe it's my weight and my stationary lifestyle? I don't know.

It is honestly hard to say. Weight, obesity and severe underweight, will have an effect on your cycle. For the skinny, if you don't have enough fat to support a child than you won't menstruate. This is only really seen in serious athletes and rarely at that. With obese women the effect is harder to see because you're honestly the best case to be able a growing child. You could become pregnant barely eat and produce a healthy child. The problem is that with increased weight comes with increased estrogen production (Which leads to more weight, kind of a viscous cycle eh?) which acts as a bit of a natural hormonal birth control by partially convincing your body that it's already pregnant. That is how hormonal birth control works.

Stress is also has an effect on your cycle. Stress can cause irregularities in a woman's cycle causing her to have delayed or even missed periods. Stress about being pregnant often causes a delayed period that causes the woman to think they're pregnant. Weird eh?

What can you do? Lose a little weight to begin with. I am a big proponent of being healthy and not having a weight restriction set on it. My wife is a little heavier than you but she's healthy. Some people's genetics cause them to be fat. It is the way it is. That just means that when you're living a healthy life style you'll still be chubby but your body will be in the same healthy state as the skinny people. So when you next see your doctor try to get a referral to a dietitian and start some physical activity. This can be as simple as walking around your block a number of time. Start slow and easy but ramp it up when you can. Walking to your corner store just around the block will be good. Do it with purpose and you would be surprised what could happen. The next week do two laps around the block. Three the next week. You don't have to go to a gym, you just need to expend calories.

Good luck.

Have you had any hormone testing done? That too might be something to consider asking your doctor about.