What Causes Extreme Stomach Bloating And Pain?

I m concerned as I have had some upper bloating on my stomach and fluttery feeling. Also tailbone pain when sitting for a while. Couple weeks ago had extreme pain and discomfort/bloating in stomach, thought it was my appendix thought I should go to hospital but went away on it s own. My period has been irregular, starting and stopping for months now. Any thoughts on what might be causing The bloating? I m scared.