Is my belly piercing rejecting, infected or an allergy?

I got my belly pierced 4 months ago, and ever since then there has always been yellow/green puss coming out of it and crusties form near the hole. Theres also a pink bump on the lower hole of my piercing, it hurts. I clean my piercing 2 times a day. The top of the piercing also sinks in the hole sometimes.
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