What to do...

My bf and I have been together for 3 years now. At first we were having sex all the time, but we've fallen out of the "puppy love" stage and that's completely okay. 
However, my bf goes through phases where he'll be in the mood for me all week, and sometimes not at all. I only see him Thursday's-Sunday's, and it's frustrating when I'm with him all weekend but we don't do it...then the very 1st day I'm not there he'll do it to porn. I'm fine with porn, I'm just so afraid it'll be more important than me. He's been on a "dry spell" for the past 2 weeks (we've done it twice) & it's been especially hard this time around for some reason. He's told me to trust him, that he's with me for a reason and that sometimes he's more in a mood for one than another. He told me we'll probably do it this weekend and seems so confident in it but it's so hard to trust him in this when I'm seeing the opposite thing happen.
Today for ex, he called at night & I told him I have pics for him. He got excited & said send them because he's taking a shower. I got really excited because I thought he was going to look at my pics & maybe do it in the shower. But, he didn't look at my pics until after he showered, & did it anyways in the shower. It's makes me feel unappreciated but he told me he's going to work on it, that it was a misunderstanding. I cried my eyes out but I just want to stop overthinking this all. Is this normal for you girls in relationships???