I'm in a very similar situation to you Vashti. Me and my girl are exclusive, she's on the pill, we've both been tested, but we still use condoms.
My opinion on condoms is that they can make average sex bad (and bad sex atrocious), but they can't stop great sex from being great sex.
When I was younger and my partners were all younger I was pretty blase about condoms. Had a couple of long term girlfriends where we didn't use them at all.
Now, I'm committed to using them all the time. It was a major adjustment. At first I was thinking "this is ****ed", but now the sex between me and my girlfriend is so good I don't even feel them. Putting one on's become part of the build up. Just use heaps and heaps of lube.
Just make it a wrought iron rule that you use them every time and you'll stop thinking about it.