How do I stop feeling so guilty?

So I'm 19 and lesbian/bisexual but only my mum and friends know so far. I've dropped hints to others over the years but even then I wasn't sure myself if I was making them randomly or for this reason. I won't go into exactly how my mum reacted but I'll just say she reacted pretty well. The main thing that stuck out was she didn't think I'd know if I was certain until I'd had some kind of experience with either gender (I've never so much as kissed anyone). I took this is as fair enough as I am still uncertain anyway.

As a result of this uncertainty I feel put off telling my dad. When I played it out in my head, I don't see him being annoyed about me liking girls so much as me saying I wasn't sure whether I liked guys or not and him assuming I don't know what I'm talking about. Now part of me feels like, ok I'll get experience with both and when I'm pretty sure I know, I'll tell him. The problem is whenever I'm around him I feel so guilty and like I should be telling him but I know I don't want to and that I'm just not ready. Too much of brain is still hanging on to liking guys for me to be certain it's all denial and I'm just a straight up lesbian.

In short, I know I have to tell him eventually and I could see myself telling him maybe in a few months. But the guilt I feel for not being completely out is exhausting. It literally rules my life. I analyse my behaviour all the time just so I can get a straight answer. Is there any way to stop feeling like this until I tell people?