I was in ur same situation. I was out for half a yr due to issues, and I was so afraid to come back because that meant I would have to give an explanation. The way I did it was go vague. Tell the person that you hav some things you are working on, and that the best thing they could do to help you is to not ask you questions. really, ppl are just concerned, and if you say that you are ok, that you are getting help, that is all that they will care about. and before you know it, they will move on.

for the ppl that you are closer to, tell them as much as you want. if the are really friends, they wont blab it all over school if you ask them not to.