Birth control pills can be good for some people but they can also cause a lot of problems, my ex-gf ended up stopping birth control after a few months due to side effects and I can't say I blame her at all, we discussed it at the time and she was on it largely because her mother suggested it, but it wreaked hell on her mental/emotional state and she also gained a lot of weight around the same time, not saying the weight gain was caused by the birth control or anything directly but more likely as a byproduct in relation to the mood stuff, 'coincidental' so to speak but still influenced by

I was happy when she got off it, we still practiced safe sex but I feel that at the time it put a genuine dent in our relationship, and this girl was one of the sweetest, strongest individual you'd ever know, At first we didn't realize it was because of the pill, but after she stopped things went back to 'normal' and our relationship was far healthier again (until the eventual break up, anyway)

admittedly this won't happen to everyone, but that's the thing with unpredictable side effects, you never know if they're going to happen and you might not even be directly aware of it at the time, imo using hormone treatment to control pregnancy is stupidly intrusive on the body's natural function despite the safety profile of such methods when you think about it, so it's kind of a 'no shit' thing that it can throw other things out of whack while still providing the desired result with high efficiency. Condoms imo are the easiest and safest option for both partners while also providing protection from STIs, though sure they're not 100% effective their efficiency profile comes down to the same type of statistic as you've just outlined and it's brought down from 100% due to things like the condom breaking from a lack of lubricant or slipping off during sex IIRC