Need to vent

So im26 weeks pregnant and this has bn by far the worst one outta my three.. I’m nauseous.. bigger and tired 24/7… and I’m high risk…. My significant other is younger than me and I’ve noticed him stay out more and more and him bn unhappy cause EVERYTHING CHANGING!”so I found out that he’s cheating with the neighbor( much younger female of course)!!! And claims it’s cause I don’t do what I use too.. we don’t have sex like we did before the pregnancy… I CAUSED ALL THIS ON MYSELF!!… why do I feel guilty behind his wrong doings!? Like y can’t I just carry/bring our child into this world safely and stress free!! Idk!!!