Friend struggling

Hi there,I think my best friend is struggling and I'd like to help him but I don't know how to deal with the situation.Basically, he doesn't know if he's gay/bi/straight. He's had sex with both guys and girls and although he didn't directly admit it he enjoyed sex with guys more. However, he's adamant that he's straight and he doesn't even want to hear about being in a relationship with a guy. So he started dating a girl a couple of weeks ago.Yesterday he didn't seem ok so I asked what was wrong. Initially he said he didn't want to talk about it but then he gave in and the told me that he hasn't felt sexual desire in the last few weeks and that although he gets a boner when he kisses the girl it's not quite right. And I honestly didn't know what to say. I don't want to make any assumptions on what he is or isn't. I just want him to be happy with whoever he is. So I told him to maybe try to watch porn to see how he feels about it and that from what he's told me it doesn't sound like he's attracted to the girl. The minute I said that he started being awkward and he dropped the conversation. So I left him be because I didn't want him to feel pressured, I just told him I'm there for him if he needs me in any way no matter what.Do you think i've done ok? Any advice on how I can deal with this? Be better support for him?Thanks!