I spent the next 30 days constantly stressed to the extreme as well as anxious. 

On day 31, I did get a 4th Gen blood test from a lab back home in nz, which came back negative for both hiv and syphilis (EIA)

On the 45th day, I took another 4th Gen hiv blood test with negative results for both hiv and syphillis. Also took a urine test which came negative for chlamydia and gonorrhea. All that  was 4 weeks ago.

The reason I really worry is in these last 2 months I have caught cold 3 times. The first cold (2 weeks after exposure) started with a sore throat and healed in 5 days but the fatigue stayed for another 10 days. The 2nd and 3rd cold infections were similar and healed normally within a week (no extra fatigue). Now I understand that my constant extreme stress could have caused my immune system to dip hence catching all these respiratory viruses, but I'm still worried that it's HIV responsible for these frequent colds.

Do I have nothing to fear in terms of HIV? Am I in the clear? Sorry if the question is stupid.

The encounters you describe were virtually no risk for HIV and low risk for other STIs. Most CSWs do not have STIs, including HIV and most single exposures to  infected partners do not lead to infection. HIV is not transmitted through receipt of unprotected oral sex and condom protected vaginal sex is virtually low risk as well as long as the condom remains intact.   Oil weakens condoms but despite that condoms often do not break and yours apparently did not since when condoms fail, they break wide open.  Microtears are an urban myth. 

Your testing provides proof that you were not infected.  Your 45 day test results for syphilis and HIV are conclusive and prove you did not acquire these infection.  Your urine tests for gonorrhea and chlamydia likewise prove that you were not infected.

Your recent colds are a matter of bad luck and do not raise concerns that your tests were not reliable.  Please don't worry - you are in the clear.  EWH

Could the white liquid like substance I found near the inner rim of the condom after vaginal sex be vaginal fluid? If it made contact with my uncircumcised foreskin could that have been enough for a possible infection to take place?

I realize I'm negative on all STDs and trust the science now, I'm only asking the question for my own knowledge.

Thank you so much for all the help you provide here and have a lovely rest of the week.