I think it was on topic, because you used to the words "permit" and "allow" in OP. I do not think that your partner should have a right to permit or allow you to have sex with others - it is your life and the choices are yours; true love is non-possessive anyway, so people should not control their partners' sexual choices. However, people also have a right to sexual safety, and, as a corollary, have a say in what you do, sexually, with others. I assumed that you used the words "permit" and "allow" in that sense, and hence the mention of condoms was on topic. If, however, you used the words "permit" and "allow" in any sense other than "have a say in sexual safety", then you contradicted yourself. Your lovers should not be controlling you to the point of permitting/allowing things in any sense other than by reiterating your responsibility for their sexual well-being; nor should you be controlling your lovers' choices, in any sense other than having a say in sexual safety. Your title uses the word "force" in a way that demonstrates that you are clearly against such use of force; then, by extension, the only permissible use of the word "permit" (no pun intended) is in the realm of sexual safety.

Back to OP - try to look forward to better days rather than look backwards to lament opportunities and connections not pursued due to the belief in monogamy. Otherwise it will be too depressing a walk down memory lane - I can tell you, given that I spent close to two decades total in monogamy. It is incredibly depressing to think both of what you lost and what your potential partners lost due to your belief in monogamy. Way too depressing.