Horrible diarrhea - need medical advice?

hello, i've been having horrible diarrhea for the longest time. i have it off and on and its been happening primarely in the past 3 months. i have to diarrhea frequently and i have been farting alot. i dont eat obsessively, and i do eat things that are good for me. but once in awhile ill eat rich foods, e.g cheescake. my mom says these give me diarrhea and that maybe im lactose intolerant? i honestly have no clue, but before when i used to diarrhea i had stomach/abdominal pains.. now i dont, its like 2nd nature now kind of like pissing i just go when i have to and its over. not usual i dont think and nothing works to calm it except getting a warm shower will keep me happy for 2 hours then its back. when i eat dairy foods i do seem to get diarrhea but it stays for like 3 days? im thinking that stuff is stuck in my system and my body is doing a poor job at getting the rich food stuff out, thus giving me diarrhea. but as i said im no doctor, i need help please.