I am in the same boat, asked the same question in my first post here and have been told that the risk is so low for contracting HSV-2 orally from giving a man fellatio that a condom is not necessary - much much more true since he's using the meds. Here's what was said there:
http://www.medhelp.org/posts/Herpes/Did-I-put-myself-at-risk/show/926760
Since then I've read a lot more research and the HSV2 virus very rarely ever goes from genital to oral. It's not transmitted through the semen - it's transmitted from contact with the virus through shedding or an open sore (his) onto mucous membranes (your mouth). The type 2 virus tends to stay in the genital area, whereas the type 1 virus does tend to transmit between the oral and genital areas more frequently.
Good thing you are still using the condoms for intercourse though, since although your risk is very low, there is still a risk.
Hope this helps clear things up.