Cheating boyfriend?


So my bf told me months ago that put in mind he’s a construction worker so has to go to material yards to order material for jobs/ clients, that a certain woman that worked there was flirting with him for weeks and asked him out on a date, supposedly he said he has a gf he loves and lives with, regardless he didn’t tell me that till weeks after when we were fighting to I guess make me jealous..which don’t know why he’s keep it a secret and say something after we were in a heated argument, but anyways said he wasn’t interested and told her that and loved me and would never deal with her and go through someone else when ordering material.. I forgave him for not telling me right away and months later when we were in another heated argument brought up the girl again and said she is Engaged and cane up to him flaunting her ring asking if he liked it which is weird... why would a girl that got shot down still be taking to the same dude saying that.. and already being engaged months later weird.. but he kept that a secret that she was still bothering him Bc he didn’t want to make me mad but waited to tell me when we were fighting.. he’s been mean to me lately and being different not giving me attention.. when I said I was going to confront her and wanted her name he would not tell me like he was protecting her, guess I’m asking should I be worried there is something going on there he’s lying? Thoughts?