Dating for 7 months, bf doesn't let me blow him

Okay so I've been with my boyfriend for 7 months, we're best friends and love and trust each other very much. An amazing relationship. We've only had sex 4 times, we're still pretty inexperienced and we were each other's first sex partner. Thing is, I always thought it'd be hot to blow someone and give them pleasure through that, but whenever I ask him he doesn't seem too keen on the idea (when I wish he'd get super excited about it), he tells me he'll let me blow him with the condom on, but then he changes the subject and I just let it go. I've asked him before why he's so weird about this and he told me he doesn't know why (he seemed pretty honest). It's not a big deal to me that he won't let me do it but I expected him to be excited about it and I want to know what the problem is. Ps.: he's Catholic and very sweet and gentle, and though he likes sex, he can be shy sometimes and there are even some sex related words he doesn't say, so I think it probably has something to do with that. Anybody has any idea what might be going on? I kissed and licked his penis a few times but stopped because of what he had told me, plus he seemed a bit tense as I was doing it.

Update: i hadn't asked in a few months since he had made it pretty clear that he doesn't feel comfortable with that, but the subject came up in a conversation this month and I asked again and he seemed excited about it and told me he had never said no at all