Can't really say unless you provide us with more information. Things to consider when calling a 3-bet are:
- Villain's range
- SPR
- Position
- Skill edge
If villain is opening too much call wider. If villain is opening not enough call tighter. If villain is playing a broken stack, 4-bet shoving becomes an option with more
hands. If the effective stacks are very deep, calling with speculative hands like A5s and QJs becomes more profitable because of the implied
odds of these hands. If you have position on villain you can call wider because you'll have an easier time realising
equity and villain will have a harder time.
Now it could be that you're already doing everything stated above and you're losing money post-flop. Since I don't really know anything about your tendencies I can't really comment in that. 3-bet pots play different from 2-bet pots because ranges tend to be stronger and SPR is lower. If you feel like you're getting stuck on the right play a lot specifically study 3-bet pots a time and make it your primary focus when playing to.