A and B (& H) are antigens (proteins) found on the surfaces of red blood cells (and some other tissues). The ability to form these antigens on the surfaces of red blood cells is governed by genes inherited from parents. The pattern of genes we have is called genotype and the form in which it is expressed is called phenotype. It is the genotype (genetic make-up), which decides what the blood group (phenotype) will be.
There are four possible blood groups in the ABO system: AB, A, B and O. Blood group A individuals possess A antigen on their red cells and have naturally occurring antibodies (anti-B) in their serum that react with group B and AB people. Blood group B individuals possess B antigen on their red cells and have naturally occurring antibodies (anti-A) in the serum that react with group A and AB people. Individuals with group AB possess both A and B antigens on their red cells and produce no naturally occurring antibodies. Finally, individuals with group O have neither A or B antigens on their red cells and have naturally occurring antibodies (anti- A and anti - B) in their serum that react with red cells from group A, B and AB people.
A blood type has the most variation in subgroup of any of the ABO blood types. There are about 20 different known subgroups. A1 and A2 individuals make up the vast majority of people with A blood type, all other subgroups equal less than 1% of As. A1 and A2 are interchangeable as far as transfusion purposes are concerned. There is no problem in conceiving and you need not be anxious.