Any suggestions??

My last period was on dec 27th 2014
On January 16 I spotted for about 5 days didn't need a pad or anything it was just there when I whipped and it would come n go nothing compared to my normal periods.. 
The thing is I don't m ow how long my cycles are its either 28 or 31 days long.. With that being said I still haven't gotten my period.. 
I took a hpt on the 22nd which would be 2 days before my period due if it was a 28 day cycle.. What are my possablilies of being pregnant??  Should I test again? & when?  Can that bleeding I had earlier in the month be inplatation bleeding?