Last night I had a hookup for the first time. I told the guy I wanted him to use a condom, which offended him because he was like, “Why do I need to use one if you already have an IUD? Do you think I’m some STD-ridden guy?” I told him I just don’t know him that well. Either way it was fine in the end, he put it on and it was a fine night. Now I’m thinking, was I being a pushover?


No. Firstly, no means of contraception is 100% effective; stacking them further reduces the likelihood of unwanted conception. Defense in depth is your friend.
Also, sometimes people can catch something without being aware of it. He might have an infection he’s not aware of. You might have one. The condom protects both of you. If you want to do it without, get yourselves tested.
And all of that is under the assumption that everyone is honest and has the best of intentions, which… isn’t always the case.
Not just sometimes, a lot of the time. STD’s are often asymptomatic, especially in men. The majority of HPV infections have no symptoms, but they can cause cervical and other cancers (and warts!). Even with HIV, an estimated 13% of people who have it don’t know they have it (per hiv.gov).