My husband has been taking Viagra...

I'm currently 33 weeks pregnant with my 3rd child. My husband and I haven't been very intimate this pregnancy and I recently caught him taking Viagra one night after work. I asked him what he was taking and he pretended not to hear me. We didn't have sex that night. Well tonight the bottle fell out of the cabinet when I was grabbing some Tylenol (pregnancy aches and pains) and I've discovered that it's empty! I'm not trying to get worked up over this or let my mind wander too much here. Should I confront him about it? We haven't been having sex, so I'm not sure what he's been up to...let alone why he needs it.