my sister had to go back to work when her baby was 6 months old.. she never wanted to but like yourself had to.
my nephew is now 13 and is, thank god, thriving.., he mixes with everyone and loves people.. however he is still vert close to my sister.
you will be the one who tucks your baby in at night the one who spends every weekend and every evening with your baby.. believe me my nephew knows that he is so so loved and he has such good social skills.. mym sister has always kept him occupied , she has given him all the time in the world.. also remember babies love other babies and kids, they love stimulation.
do not geel guilty you are obviously a very loving mum what more could a child want