Folding to value bets, calling bluffs

Do you have a hand history to go along with your question?

Your bet sizing could be making your hand obvious, or you're just playing into the wrong types of players in the wrong types of situations. Don't bluff a calling station, and don't pay off the nits.

Very hard to tell without knowing the sample size you're talking about. Anything can happen in the short-term. If you're talking about a decent sample size of at least 5k hands or more, then it's probably something you're doing and you'll need to adjust.