Pains but no cause

I've recently had tests including bloods and literally nothing comes back despite me being in pain all the time. Usually in my stomach. I've had tests a few years back and the same thing. I genuinely am in pain but my family think I imagine it. Could this be an autism thing? I try to keep busy and it can help with the pain at times but it's always there and can make me feel rough at times. I had tests a few days ago and today the GP said it's all come back okay. Confused and feeling like I just graduated from the school of muppets.