hormone levels low can be passed down thru family or due to other things in your life, like stress or being underweight etc
My youngest always had to take blood tests for pregnancy and she had her still born daughter( she had no spleen) with the marriage ending in divorce.She was terrified the whole time during the next pregnancy.Went to counseling that her doctor suggested based on income.
Pregnancy doesn't stop you from going to school,you just need to make sure the school knows so they can work your class schedule around the time you will need off.
You are engaged, you need to find out right now if you are pregnant. there are choices the two of you need to make like move the wedding up or back( two of my daughters moved theirs back to after the baby was born).
I understand you are worried about what your family will think and feel. Do you think your family doesn't realize you are having sex outside of marriage and that is what is worrying you? or is it having the baby outside of marriage?...or as I put it to my granddaughter, her fears and worrys about family feeling were really her own feelings being unsettled over the choices she had made and she was reflecting them back on the family.
I think you will find your family being very supportive and loving, that they will be concerned of course but more with you having what you need and being taken care of.
BUT first go have the blood work, the worry and stress of wondering isn't doing any good and you can't move forward and make good choices without that knowledge...let us all know the results so we can be supportive of you here.