Her period is two months late but her periods have been already irregular

Hi my gf and i are both 19yo this year, we had protected sex twice so far, once in december and once in january. However she has missed her period  for two months alrd. Her period has been irregular over the past months, but we are afraid she is pregnant this time. So far there hvnt been any pregnancy symptoms, she says she feels fine, theres only the missed period that is worrying us. The sex in december was about a week after her ovulation period. A few days ago, she said her period came, however it was abit diluted and slightly brown. I did some research and came across implantation bleeding, which is commonly mistaken as a period. Now we are very worried that it is actually an implantation bleeding. However, she still hasnt had any pregnancy symptoms yet. We are trying to avoid taking a pregnancy test because we are afraid of what the results may yield. Pls can someone enlighten and help us out? Is she pregnant?