Why am I so evasive on the topic of girls.

Whenever my friend talks about my interest or type in girls or anything about them in general, I go all evasive and speechless. I literally can't have a confident conversation about my interests to my friends.

Whenever a girl makes a suggestive expression I again get all weird and shutdown any conversation at all.

I don't have any issue talking to girls about pretty much anythings. Its when it gets into something further I get all weird and evasive.

I’m the same as you but I’m a girl and this happens with guys. I can have a guy friend but if he escalates things I will shut down. In my case it's cos I have avoidant attachment style (fear of intimacy/ emotional closeness). Probably your case as well, I suggest u read about it online, see if you relate to the symptoms

Its nice to hear someone having similar problems.

I just researched a bit and some of the symptoms made me cry.

I don't show any emotions at all. Its very rare I do.

I am extremely scared of rejection. Whenever I think of myself getting close with a girl, I never feel I am worthy of it at all. I feel like I don't deserve it.

I don't know how to solve this issue at all.

Are you under 18? If so, you're likely just not ready for all that yet. And that's okay.