Alfie
Everyone's different but my experience at least is that it can take a long time to get back to normal after coming off the pill.
I came off Microgynon about a year ago, for the first 6 months it was all over the place with v long cycles and sometimes more normal, then it started to settle down in the second six months, with my cycles being something like 40, 38, 34, 34, 32 and 29 days (most recent last!) I think it is now settling down into pre-pill pattern (hope so as we're in month 1 of TTC!)
You could be pregnant (hope so!) but there again, it could just be your hormones all over the place and making you feel these symptoms.
The problem is that you probably don't know whether you've definitely already ovulated this cycle. If you don't know whether you ovulated, you don't actually know whether your period is "late" or not. You usually get your period about 10 - 14 days after ovulation, so in theory it could be that you perhaps haven't ovulated yet, or perhaps only ovulated 5 days ago, for example. So even though you think your period is well overdue, it actually isn't, and it is too early to test. Have you been having intercourse very regularly throughout the 38 days, so that in theory you could be pregnant even if you ovulated much later than expected?
If you did ovulate at the "normal" time and you really are several days "late", then it's unlikely that you are pregnant I would have thought, because tests pick it up at this stage?
Perhaps best to hang on for a few more days and try again or ask the doctor to do a blood pregnancy test.
If you don't already, you might want to use Fertility Friend (google it) to actually chart what is going on with your cycle as it starts to return to normal. Then, at least, you'll know when you ovulate. I didn't use Fertility Friend till recently, but I know if I had used it as soon as I came off the pill, it would have shown great variations in when I ovulated each month, as things got back to normal.
If your ovulation date is erratic until things get back to normal then the best way to get pregnant must be to do the deed every 2 (or three) days throughout the cycle - then you'll be in with a chance whenever you ovulate!
HTH
Bumpsx