1. kissing someone is not infidelity
2. having sex with someone when not in a committed relationship is not infidelity
Neither of you cheated.
You both sound pretty young and prone to drama.
Stay where you are living - away from each other - and start counselling (particularly if you are not already in post-abortion counselling - you don't seem to be managing that well). Perhaps as a couple, perhaps individually as well.
Minor blips can be worked out but yeah, you actually have to both work at it.
Take some time to work through it all.