I think that a doctor would be the best source of information regarding what to expect physically from the pregnancy. He/She can also give you an idea of your hormone levels, etc. You may have to monitor that closely.
Medical questions aside, there are tons of questions that you have to ask yourself before going for it.
How stable is the relationship, financial planning, housing considerations, if you had to raise the child on your own, would you? If he had to raise the child on his own, would he? External resources for childcare. Compatible parenting styles.
I do not want to sound like a blah poster, but I think that "i"s and "t"s should be dotted and crossed as much as possible before making such a decision of love and responsibility.
Wisdom and best wishes.