Starting mid-cycle is completely fine. I don’t know who told you it’s not recommended, but they should not be the ones giving you any advice. Side effects can happen regardless of when you start or how long you use birth control for, they aren’t connected. The adjustment period for birth control is 3-6 months, in which you can experience increased side effects. Usually after the adjustment phase these side effects will get less, but you will not be immune to them. Some people don’t experience side effects, others do. Cramps are a normal side effect of birth control.
This {6z5uXrNN8} might be of help to you as it explains a lot about the pill and birth control in general. There’s also a section about bleeds, as you don’t experience an actual period (and as to why it doesn’t matter if you stop bleeding altogether).