My Metabolism is not working!?

I have just recovered from H-Pylori. But with the sickness and without it now I still can not eat! I get hunger pangs maybe twice a week. I can go two days on a banana. I gained twenty pounds from NOT eating. I'm trying to lose the weight ( i'm only 27) and I can't lose it. I have tried eating little bit at a time, but I'm FULL all the time. I need to lose this weight. I need to be healty again. I'm the only person who gains wait from not eating. I eat only protein shakes and bananas. I may have soup twice a week. I cannot live like this. In order to speed up my metabolism and digest food again what do I need to do?. Should I re instate good bacteria from a probiotic regiment?. Take enzyme pills?. Any advice. I'm at my wits end. It's my high school reunion in two weeks! Not to mention I hate feeling full like I ate a 5 course meal and all I had was a gl of milk!