I agree with sillymistake - we can't give you odds, but given your age group, you should definitely test. Your chance for chlamydia is a lot higher than HIV.
Also, there's gonorrhea, NGU, HPV, herpes, syphilis, etc. You should consider wearing a condom. If you haven't been vaccinated for HPV, you should talk to your doctor about that. It's estimated that about 90% of us will get that at least once in our lifetimes. The vaccine can really reduce those chances.
First, if you are concerned with HIV and had an actual exposure (which is ONLY unprotected vaginal or anal sex or sharing IV drug needles) and you take a 4th generation test at 28 days or beyond after the event or any other test 90 days after, you do not need to retest. Those tests are accurate and you can count on the results so multiple tests and excessive worry isn't necessary. FYI. Why not use a condom? That would make sense given the number of times you have had unprotected sex.
Obviously, chlamydia can happen from unprotected intercourse. Got any symptoms? Here's an article to check out. https://www.webmd.com/sexual-conditions/chlamydia#1
No point in giving odds really. You have been at risk and your age bumps it up (statically). Why would you have a HIV test but not test for all of it?