Welcome to the boards, _bee.
It's normal to have some discharge at any time, as that's how the vagina cleans itself. We have more information on what kinds of discharge are healthy and what kinds are a good idea to check with a doctor here:
Honorably Discharged: A Guide to Vaginal Secretions. Too, if your partner is ejaculating directly inside you (rather than into a condom), you're likely to see some differences in your discharge for the following day or so because your body will be discharging the semen as well.
If you're using any kind of hormonal birth control (for example, the pill, ring or patch), you won't have any fertile days. One of the main ways hormonal birth control works is by preventing ovulation: so, if you're using your birth control correctly, you're not going to ovulate and you're not going to be fertile. If you'd like more information, we have a thorough description of how it works:
How do birth control pills really work, even during the placebo period? (that question was about the pill, but the patch and ring work the same way). The information your app is giving you about a "fertile day" is completely irrelevant for anyone on hormonal birth control, and I suggest you only use apps like that for tracking the dates that you get your bleeds, as they can't tell you anything else. (Too, even for a person who isn't using any hormonal birth control, "fertile day" is very inaccurate: for a start, while ovulation happens on one day, a person is fertile for several days around that time, and secondly, an app can only accurately suggest when a person ovulates if it asks for detailed charting data about temperature and cervical mucous every day.)
Bloating is unlikely to be related to any kind of sex. It can be caused by various lifestyle or health issues, or connected to the menstrual cycle. A little bloating occasionally is nothing to be concerned about, but if it's bothering you or happening a lot, the right person to ask is an in-person healthcare provider.
If you're still concerned about pregnancy even though you're on birth control, do you think you need more information about how it works and how effective it is, or do you think you'd feel more secure by using a second method as well, like condoms?