Can Stomach Problems Cause Severe Headache?

Hi, I've been having severe headaches which seem to be related to a stomach issue. I have been having severe gas/bloating which I'm unable to release. When I'm able to finally burp, it makes my headache slightly better for a short time. I have seen a GI specialist and at this time we have come up with nothing. This has been going on for a month now with me have this almost everyday or with a 1 day break in between. What other things should I look into? thanks