specifically when complimented on your general appearance?

in the past i have received compliments on my outfits, purse, jewelry, etc., and i don’t have any issues (any more than usual) responding to those. but lately i have gotten complimented on my appearance, being told that i’m pretty or they like my hair or something. i normally just smile and say thank you but i feel so awkward for some reason. is it rude not to compliment them back?

i’m definitely putting too much thought into it but this is a very new concept for me. i grew up a really overweight kid and didn’t start losing weight until a couple years ago. i’ve never just randomly been told i am pretty by anyone other than a couple of close friends (and even then i didn’t know how to respond because i didn’t believe it). anyway, not getting into all that because that’s not the point of this post. but seriously what do you say? how do i be normal??

also……. how can i tell the difference between a general compliment and someone flirting with me..? because there have been a couple of times when i have been complimented when i’m with a friend and when we leave my friend will ask me why i didn’t ask for their number or something and i will be like what?? could i have done that???