I agree with Lil. If you've improved since being home-schooled, then stress may be very well making you worse, and you should look to ways to control the stress. Maybe a lighter class load? Maybe in-school counseling or tutorting? Maybe private therapy? I don't know if your mom is a pusher--always on you about making good grades, better grades, perfect grades, etc--but if she is, then she may be causing a lot of your stress and she would need to attend counseling with you to learn how to back off. In Japan, land of the grade-obessed mother, they have a high rate of bowel problems, depression and suicide in kids, so parent pressure (including from dads or other relatives) can lead to a lot of problems.
If you're about the same as before, then you probably should continue to stay at home until such time as it gets better or you go to college (college is easier because you can skip class pretty easily and you don't usually have to be there all day, so you can come and go to classes as you need to, then retreat back to your dorm room or bathroom). A lot of colleges now also offer online classes, so you only have to meet for class every now and again, and most of the work you do on your own. In fact, there's one college out in California that's very liberal arts, and students design their own course plans and study on their own, just occasionally seeking advice from their counselor. It takes a lot of drive to stick to such an unstructured course of study, but it allows you to do it at home and it allows you to study a wider range of interests.
If you miss your friends and getting out of the house for school everyday, is there a compromise? Maybe you can go to each class (math, english, science, etc.) once a week and do homeschooling the rest of the time? That way you could get to see your friends a little most days of the week, and get to talk to your teachers, but only have to endure small amounts of time away from home. At the very least, I don't think you should try going back full-time at first, not until you see how your guts are. Can you do half-days, as in just afternoons? That should allow you to quit stressing as much and maybe you'll be able to ease back into a normal school day. Also, the spring seems to be a better time in the school year, because even though there are end-year exams, the weather is getting nice and everyone seems happier and less anxious.