Missed period now pos OPK

So my last period was 19th Jan and I have not had any bleeding or spotting or any signs of AF since. I'm now on cycle day 51 so I did a HPT yesterday and it was negative so I thought id try an OPK which got a positive so I guess it's just safe to say that I completely missed February's period for whatever reason and now I'm ovulating? I have a sharp pain on the left side of my belly. Im so confused😖