I feel the same way too sometimes. It's hard to say why, where it's coming from. But it's not your fault you are feeling this way.
And I do believe it's possible to "absorb" in a way negative feelings from your environment or even this site, without being conscious of it..
Regardless, your feelings are valid and there is a lot of paon in them...
Just hope you'll be able to see yourself as worthy of love, because you really are