Every piercing I've ever had has never healed, no matter how well I cleaned. My body just rejects piercings and there's nothing to be done about it. At the time I removed my eyebrow piercing, it had already started migrating to the surface (like how a body ejects a wood splinter) and the hair in my eyebrow was falling out. Never came back either, so I have a nice line on one side.
There are still some things you can try though...
You can try changing the jewelry, either the size or the type of metal. When you change it, use spectrojel (see below) to disinfect and insert it smoothly. You're not really supposed to change jewelry during healing EXCEPT if the source of the problem is the jewelry itself. Switch to a smaller gauge because sometimes the gauge is too big and it's putting pressure on the wound so that it can't drain properly. You can also try changing the jewlery to pure silver or gold because some people are allergic to stainless steel. Plus gold and silver are naturally antibiotic. In my case, after holding out for more than a year, my piercings kept crusting and getting irritated until finally keloid scar tissue started forming and I said fuck this and removed them. I didn't want to have permanent damage. Even my ear piercings did that.
For cleansing, I used plain spectrojel to clean my piercings, after trying a million different products. Spectrojel is the best unscented, hypoallergenic, disinfecting cleanser out there, even better than cetaphil. Get a shot glass and put it against your piercing with warm water in it for about 5 minutes to soften the crusties. Then apply spectrojel with a qtip, and gently move the piercing back and forth so that the jel goes inside. Then rinse thoroughly. If it's swollen, raw, or irritated, then follow this up with a shot glass of salt water. Salt water is also best if the piercing site tends to be moist and "juicy" a lot. It will astringe some of that fluid out.
Only do the spectrojel once a day (before bed is best) because more than that can be irritating. If the crust is always there then you can soften it with salt water and remove it however many times a day you need to. Do not use polysporin or any other antibiotic ointment because it contains bacitracin which does not just kill external bacteria but it also kills your body's own immune cells in the wound, and slows healing.
Stop the sexual play with your nipples because that is just going to make it worse. I love nipple play, but mouths are filled with bacteria and putting that on a raw wound is not a good idea. Likewise, don't rotate the piercing or move it back and forth unless you are cleaning it. If you wake up in the morning and the piercing feels stuck, then just leave it. Every time you move it you irritate the wound, and your hands are contaminating it.
If you try all this and it's still not healing then it means your body doesn't like its nipples pierced and you should remove them before it becomes keloid scar tissue. If a lot of scar tissue forms then you'll lose nipple sensation and you don't want that!