Dont really know whats going on..?

Hello ok so im a girl, im 18 years old and for the past three years I've had stomach issues. The weird thing is, that it only happens during the fall and winter months.. I dont know why I eat the same things during fall and winter. I've been to the gi doctor and I've had literally every test done, colonoscopy, endoscopy, ct scans, sibo test, the list goes on. The only thing that came back saying I had something wrong was the small intestinal bacteria overgrowth test and the doctors put me on antibiotics for that, ive taken 4 of those tests and they all came back positive so ive been on antibiotics 4 times and they didnt really help and the doctor said i cant be on antibiotics all the time. I dont think the only thing wrong with me is having SIBO.. I take probiotics twice a day and I also have a mild form of gerd so i take nexium once a day. I used to be on a very small dosage of prozac but I stopped using it early this year it didnt help and I dont think anxiety has to do with my stomach, the only thing im stressed about is my stomach. I dont understand why I get symptoms during the winter and fall months. I feel bad around october - february ish and then I feel fine during the summer and get symptoms again during fall and winter. The only new symptom this time is that I have nausea, the past two years I havent had nausea. It sucks because Im 18, I want to go live my life and get a job and go to college yet I cant because I have to worry about using the bathroom or throwing up all the time. Do you think it could possibly be allergies? I dont know where I'm going to with this question.. I guess I just want to know if anybody else feels bad during the winter and fall months and if they've found out a reason why or how to help not feeling bad? I cant be like this for the rest of my life I cant just stop doing everything during winter because I feel sick. This has been making me really depressed lately because I literally cannot do anything.