Yay, nats!! I hope this is it for you! I would keep using the opks for a few days though just to make sure. If you go a few more days and no +, then I would say for sure you just missed the surge this month. If you get a + in a day or two, though, you'll know to BD again!
AFM - Things are getting a little easier here... however, I fear we gave Quinn a bottle too early (been pumping and bottle feeding sometimes to give my poor nips a break and let daddy feed) and the last couple times I've put her on the boob she only latches for 10 seconds each time before screaming and then repeating until she's done eating. It's not the end of the world to have to bottle feed only, but it is a little more work.
There's really all kinds of things that could be the issue. From latch issues to fast letdown to slow letdown to low supply (which it doesn't sound like to me if you're pumping plenty). If it's slowish letdown, you may want to try a supplemental nursing system to get her back on the boob. Just start with it until you feel the letdown and then take the SNS tube out of her mouth. Or maybe hand express until the milk starts flowing and then put her on the boob.
I'd personally try anything to keep her nursing because exclusively pumping sucks balls, to be honest. There are also bottles (Breastflow and Medela Calma, I think. From what I hear Breastflow is better) that are expensive but, to my understanding, flow more like boobs, so makes the transition between bottle and boob easier on LO. If she won't nurse, make sure you pump at least 8 times a day to keep up that supply the first several weeks. I know that sucks but it's really important in the early days if you want to continue producing enough.
If she gulping and sputtering/choking while on the boob, you may have a strong letdown that she doesn't like. In that case, I'm not sure what to suggest other than leaning back while you nurse so that your letdown has to work against gravity. Have you seen a lactation consultant? They should be able to assess the exact problem and should have some suggestions for you.

She may even have a latch issue or a tongue/lip tie that is causing her to not be able to transfer milk from you very well (which leads to frustration and screaming). With you saying that your nips are sore (are they cracked?), it makes me think there may actually be a latch problem. Maisie nearly killed my nipples in just 2 days because she wasn't taking enough of my boob into her mouth with the nipple. Once I got her to latch better, it hardly hurt at all, even though I had cracked nips. But then she started refusing shortly after anyway because of my low supply. Hope you're able to get it figured out! You may also want to look up your local La Leche League. They generally have a facebook page where you can ask questions and find out when their next meeting is. They're usually quite helpful. I didn't do it after having Maisie but have joined since becoming pregnant again and so far they've been quite supportive and helpful for me.
Oh, also, massage the boobs while you pump and try hand expressing after you're finished pumping. That'll help empty the boobs and keep up your supply better than pumping alone. Babies (with proper latches) remove milk better than pumping or hand expression but hand expression empties better than pumping.
I know this is unsolicited advice so do whatever you want with it, or not.