<human>: Can you summarize the given text in a few sentences?

My partner works in a bar in is frequently out at all hours. He tends to go to friends houses and fall asleep there after work. As far as I know, I don't have any specific need to feel jealous, but I have been getting more and more taken up with it. So much so, that I can't concentrate, feel physically ill (queasy,heart racing and stabbing headache, constant lump in my throat) and am ridiculously volatile with my moods. I hate myself like this. When I'm thinking rationally I don't see any signs that he might be cheating (other than the staying at friends houses thing..) But I for some reason started going through his phone and there are messages between him and 3 different people over the last 5 months that could be misconstrued. It's mostly stuff like 'Had such a great time with you ;)' or 'Miss you'; 'Can't wait to see you'. 
We've been together over 4 years and have two kids (3,1).  I'm not very confrontational and any discussion about changing his after work behaviour has not gone well. He gets annoyed and doesn't say anything and I start getting very passive aggressive about that and loose my train of thought, try to back-pedal because I'm terrified he'll hate me if I say all this stuff. He doesn't know I went through his phone. I have never ever done that before and feel terrible about it. I'm feeling lonely and lost in this.
<bot>: recently developed jealousy issues, went through bf phone(why oh why), feel sick, even though no conclusive evidence of any wrong behaviour