If you had unprotected sex with a girl over a few months but didn't cum inside her what are the chances you would catch chalmdyia?

Not protected. You have a good chance of contracting it if she has chlamydia. Whether you ejaculate into the vagina or not has no effect on sexually transmitted diseases and often does not prevent pregnancy as well. If you do not know the STD status of the girl, and even if you think you do, having unprotected sex places you both at risk and risks pregnancy. Pre-ejaculate has sperm. See your doctor.
Highly likely. Chlamydia is an STI that is quite contagious. It is spread by unprotected sex. If your partner has been diagnosed with chlamydia, it is important for BOTH OF YOU to be treated. If you have not been tested and are concerned, it is advisable to be tested for chlamydia as well as other STI's so proper treatment can be prescribed.