Pain when lying down

Hey. I have this problem for about year and it got worse.

So, before, I woke up everyday with pain in lower section of my belly. When I stood up, it was gone. But now for the past 3 months, I have "constipation" ( I have bms, but really small amount) , and some other stomach problems, the pain comes back Everytime I lay down during the day, never at night. Only mornings and during the day. After I stand up, I need to go to have bm. Then everything is fine. What this could be

Go see a doctor

Go see a GI doctor