Steve is a bit of a serial monogamous. He has had multiple girlfriends, but most of them (Connie Ferrari and Miranda Pritchett notwithstanding) have been very long-term. As in years. Right now he's with Sharon Carter, he's been with her this second time since around 2005-2006 in the comics, to give an indication of what I mean. His other long-term girlfriends have been Bernie, as you said (and whom he was actually engaged to at one point) and also Rachel Leighton (Diamondback, currently in the Domino: Hotshots series). He was with Bernie from Stern thru DeMatteis and the beginning of Gruenwald, and then with Rachel for the rest of Gruenwald (and Gruenwald had a ten year run, so....). He got back together with Sharon at the beginning of Brubaker's volume 5 and has been with her ever since.