It was a stupid lie but I have no idea why he even did it. Ive asked him and he doesn't know either. I asked who'd text him and called him (after noticing the name and number wasn't one I'd seen before) and he told me it was his dad responding late to a message he'd sent. When I confronted him about why he'd lied and said it was his dad when I know full well it wasn't, because it had been a girls name on the screen not the word 'Dad'. He told me he was embarrassed because it's a friend who's older than him, female, who's been asking him for relationship advice.
I don't understand how that would embarrass him, if he was just being a good friend then why would he tell me it was his dad and create a back story to it?
I know it was a stupid thing for him to do, and I know he loves me. I want to believe him, as I've spoken to the woman and it was true what he'd said about her asking his advice. But when I look at him my heart sinks and I don't feel like he's the same guy anymore. He says something to me now and in my head I question it.
I don't know what to do, I want to make it work and I don't wants something so stupid and small to cause everything to end. Help...

Do you go through his phone often, or confront him about his call? Is this just another suspicious incident, or the first one?

Are you insecure, or the jealous type? Or confrontational? Do you check emails?

Hard to say without answers to those questions whether he did it because of you, or your past reactions to him.

I was sitting next to him when the fone went off, the name came up and I saw it out of the corner of my eye. So I asked who it was, and then he told me it was his dad. I always trusted him, I never go through his fone or email or anything, even though I have the ability and opportunity to if I really felt like it. Its not that it was suspicious because I know everything about the situation and sorted it out. I just don't feel like I can trust him now after he lied to my face, over something so stupid. He said he was nervous and the lie just happened. I don't know why he'd be nervous I'm not the sort of person who will get pissed off or annoyed if he talks to other women.
I just feel now like everything he says will be a pile of crap, if he's late home or doesn't have a reason for being late or anything, its made me paranoid. And he doesn't get why its bothered me so much. He thinks I can just close my eyes count to 10 and it never happened. But I cant. And I don't know what to do.

You tell him, just as you have told us, how his lying makes you feel. And that he doesn't have to lie.

Then you drop it! Never bring this incident up again. I will tell you that he may have been afraid of your reaction to the truth, and he may have a point in my view, because of the way you reacted after his lie.

I think had you given him the benefit of a doubt in the first place, and not asked who called, but asked it another way, by asking "who is she"? signaling to him that you saw it was a female, he might have felt free to tell the truth, or you would have had a lot more information by which to decide if he is actually trust worthy, or scared.

Small differences I know, but if one lie makes you paranoid, and after checking your fear was unfounded, it signals that you had better be straight and honest with him about his lying, which he may never do again, because he knows you will check to see if it is indeed the truth.

You better clear the trust issue up, because it will grow out of proportion if you don't. Communications is what's key, and careful thoughtful actions. That's doesn't mean you don't pay attention though, but you may find he has fears to, about YOU.

My point is why presume and assume and get carried away, when you can talk about it.