Am I crazy?

My bf and I have been together for a year and 3 months now . I am definitely inlove , he works as a school bus driver and recently chose a different route that is more $. This route is upstate newyork ( 2-3 hrs one way ) and with nyc morning traffic he don't bother to drive back to brooklyn while the kids are at school so he rather wait. However my problem lies with his matron/ school aide. She's in her 50's (he's 27) and they spend alot of time together now compared to last year. I've noticed her texting him inappropriate things Calling him On his days off , and as a woman i can definitely tell she is interested in him since i met her . She don't like me and hate that I call him during school hours when they're both in the bus parked up waiting for 3:15. She starts making loud obnoxious noises and he don't see it as a big deal that she's constantly shooting her shots. Today we were talking and he mentioned that she confessed her feelings towards him and that she wanted to be with him a few weeks ago... how could he not mention this to me. Not to mention him starting to sleep with his phone under his pillow.. i dont want to check it because I feel like im betraying his trust but my intuition is alarming and hard to ignore. Advice ?!!!!!! Please ask questions