Really worried about HIV, after being fingered

I am an 18 year old gay man (passive) and I have been sexually active since last February. I always have sex with protection and the condom has never broken.
I am really worried about getting infected by HIV, and that is largely due to the fact that my Biology book has a whole unit dedicated to the virus and how bad it is. I have asked my partner a million times, to the point where I've started getting annoying, if he is "clean" and he's always said yes. He seems to be, too, he eats healthily and he works out but, of course this doesn't prove anything.
I am now worried because the last time we had sex he finished on my belly and then after 2 minutes or so he fingered me. The thing is, he did that with his OTHER hand, not the one he ejaculated with, so I am not even sure his finger had any trace of sperm on it. This is the only case I MIGHT have been in contact with his fluids. I have never performed oral sex and he always finished in the condom, except for this one last time.

I am really worried so I am asking for a bit of advice.

[pmdmello]

You never had a exposure, the virus is transmitted INSIDE the body and not outside.