Stomach problems question

So I started to fast a couple of months ago because I got a date to go to Basic Training, I wanted to make weight. I started and did good, lost a lot of weight, well while I was fasting I would use zyns. I’m not sure if that’s important but now a couple months later I think I have an acid problem that could be cause from fasting and nicotine and I want to stop it before I ship out. Also, I stopped because I made the weight I want, now I just make sure not to gain more weight. Anyone experienced this before?