I feel very ashamed of myself and I don't feel worthy enough to be a Christian. Can someone help?

Hello all, I have a problem.

I love God more than anything and I'm so grateful everyday that He allows me to spend time with Him, even though I'm not worthy at all. Actually, here comes my problem. I struggle with some very very dark thoughts that I don't really feel comfortable sharing because they are very dark and I'm deeply ashamed of them. I don't want them, and yet, they somehow are always on my mind. I find comfort in the known, and these thoughts I have had for a long time.

Anyway, where I'm getting is I feel like I'm not worthy enough to be a Christian, to worship God, to pray to Him or talk to Him or to even know about Him. I feel so ashamed of myself I just want to hide, I don't deserve Him and I don't deserve His love, grace or salvation. I'm very scared of going to hell because of those thoughts and the thought of Jesus saying "I never knew you" absolutely terrifies me and makes me even more ashamed of my thoughts, as if I could somehow get even more ashamed than I am now.

What do I do? I feel unworthy of even asking for mercy or grace, because I don't deserve them and I don't even deserve talking to God. I feel so selfish. I love Him, but I wish I could love Him the way He deserves..but I keep failing Him