Passing out during ibs attack

Hi everyone. I am female and have had ibs since I was 15-16 years old. I get diarrhea and bloating mainly but sometimes can get constipation. If I lift something too heavy I feel like I have "strained" my stomach and the pain starts. Sometimes I think it is related to food. I have fainted every now and then, sometimes 8-10 months apart since the age of 15. About a month ago I woke in the night with severe pain and usual pattern, I get to the loo but have trouble passing anything. I start to sweat loads, go hot and cold, vision starts to go and next thing I come round on the floor. I get up shaky and cold needing to go to the loo. Last time I hit my head on the sink which scared me but I was lucky that my husband was home at the time. Last night I woke (1.30am) with severe pain, went to the loo, managed to pass something, pain started, hadn’t woke my husband so knew i had to get to the bedroom to get help. He is not sure if I fainted. I only remember needing to get to the bedroom and next thing being aware that my head was on the doorstep and my husband asking what I needed, as in medicine/help. I have medicine called Viadil Forte that I use (It relaxes stomach) but I am not getting the warning that I used to so am not always able to use it before I pass out. Some doctors say oh its ibs, another has said no definitely not and yet another says it is the pain that causes me to faint not ibs. Does anyone else pass out with ibs? Please help me, it gets me down so much.