I don't get aroused by him anymore. Help!

So me and my interest have been doing some sexual things lately. I'm still a virgin btw! When he fingered me the first time, it felt absolutely amazing! Now it's like I don't feel what I used to. It feels great but not as good as it was. It's like the feelings wearing off? It's like the only way to get me off is him eating me out and fingering me at the same time. What do I do to feel the way I used to?