I think you need a little more length to be able to tell your hair type. If I had to guess now, I would say 4a, but...

It looks like you still have some relaxed pieces in the back, but even that may be too hard to tell yet.
APL BSL MBL WL HL TBL | porous, fine/medium strands, medium density
My Fotki!
Below: Typical PS bun