Im With my Friends Ex Boyfriend?

Hi im Tara. i live in a 3 bedroom apartment and Pregnant with my first child. 7 months. i live with my husband Gavin. hes very sweet and stuff but heres the issue. 3 years ago i met a girl named Donna. we became best friends and i found out JUST Today that she and Gavin were a thing. This has put a lot of strain on my pregnency Donna dosnt know im married to Gavin!!!!!!!!!! Should i tell her????