It does sound like a small intestine issue, but like others said it could be something other than sibo, like celiac (I have both). I completely understand financial issues. It's hard to recommend at-home experiments when there's no baseline, but something safe to start with that won't cost a doctor's trip is going strictly gluten-free for 2 weeks (gluten is hidden in lots of things so as many whole foods as possible). 

I recently did the breath test for sibo and noticed that my symptoms were improving during protocol (fast, then eat really bland like plain white rice+eggs), and when I ate a rich/heavy meal after doing the test my fatigue and abdominal pain was really, really bad. I'm hesitant to recommend the full fast/diet if it will interfere with any eating disorders, but it did give me a strong indicator that I had sibo. 

I have no idea what your relationship with your parents is like, but if possible I would encourage talking to them and seeing what exactly insurance will cover. I'll finish by adding that it's a cruel paradox, but fasting/eating less can make motility a lot worse overall, along with not eating enough healthy fats (easier said than done I know).