Hi mate, I’ve been training since I was about 16/17 and fairly seriously since the age of 20, I’m 24 now and my best year was when I was 21. Its prob my best, first glance, asset when approaching a woman.
How old are you? If your still maturing it could be part of the reason, whether or not that is the case, you may be over training.
When you say 3 times a week, do you mean you are training everything 3 times a week or doing sets of muscles, i.e. chest and shoulders on day one, back and bi's on day two etc (there are infinite others to choose from). Also, do you always do the same exercises for each muscle group?
Are you eating properly?
The joins can take a while to catch up with a new body shape and especially with new, heavier weights constantly being forced upon them so maybe dropping the weight and getting quality long sets out are best, it gives much better definition anyway and this creates a better foundation to work on than just trying to get mass to start with.
I also think girls like toned rather than massive, in general. most tell me not to get any bigger or ill look like a meat head.... like that would be a bad thing?... but hey, we're all here for the girls right, so what they want, they should get!
If it hurts then yes, stop until a later date, when it feels good again build the weight slowly. If it just aches then the sensible thing to say would be the same, however, I’m not always known to practice what I preach... but it’s up to you.
Another good tip is cod liver, i needed them for a month before i noticed an effect, their pretty good to take anyway so even if they don’t help your joints with this, you might remember your pick up lines better lol.
A last note, buy magazines, i recomend Flex and Muscle and Fitness, i subscribed to both since i was 20 and have learnt so much from them... their also the experts and im not (thats my disclaimer

)
Pash.