Cycle Irregularity

Bristee
Currently on my 1st month off bc. Haven't had af in 7 weeks, (so technically I'm 3 weeks late). All tests have been bfn, but I'm not surprised, since I know it usually takes awhile for your cycles to get straightened out. 
But just how long?? I just want to know what my body is doing. How long until I should make an appt with the Doctor to see what's going on? I don't want to be wasting anyone's time if all they are going to say is "it's going to be awhile because bc messed up my cycle." I'm going crazy here!! Any advice/past experiences/etc is very welcome!!