If I do not ejaculate into my girlfriend during intercourse, can I still get chlamydia?

Absolutely. It is not the ejaculation that is the problem. It is the penis in the vagina. Condoms will prevent this. Be safe, be responsible and be informed. See my answer on trichamonas.
For sure. If your gf, or any sexual partner, has chlamydia and you have unprotected sex with her, you can certainly get it whether you ejaculate or no..