Hypospadias might slightly increase the risk of some STDs, such as gonorrhea or chlamydia. This has never been studied, but if there is an effect, it probably is minor. Hypospadias almost certainly increases the risk of other (non-STD) infections, including non-sexually acquired urethritis due to vaginal, oral, or anal bacteria. The symptoms may mimic STDs. To the extent that any inflammation increases the risk of HIV in an exposed person, I imagine that people with hypospadias-related infections might be at somewhat increased risk for HIV. This also has not been studied, but if there is such an effect, it surely is too small to worry about. Select your partners with care and use condoms consistently, then don't worry about HIV.
I cannot predict the likelihood that one or more of your partners was at HIV, regardless of whether the last one didn't ask you about your HIV status.
Although your overall HIV risk is low, anybody with your sort of sexual lifestyle should have routine STD and HIV tests from time to time, such as once a year. Since you probably haven't been tested in a while and are about to start a new (committed?) relationship, this would be an excellent time for you to visit a sexual health centre. Collectively, Australia's SHCs probably are the world's best STD clinic system. (If you go to the Adelaide, Melbourne, or Sydney SHC, give them my personal greetings.)
Sorry I misunderstood, but I don't have more to add at this point. In view of your sexual lifestyle, I see no reason for HIV testing more than once a year, regardless of specific exposures (unless you learn for sure that a partner had HIV). But if you will sleep better having another negative result, it's fine with me to be retested 6 weeks after your last exposure.
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