hmmm, that could be a problem.
Children born from donor insemination need to be treated similarly to adopted children, ie explain as young as possible and expand detials slowly as they get older.
More difficult to deal with you DD having so much time with her father whereas junior would have none at all unless he was prepared to act in loco parentis for at least part of the time.
Re meeting someone, I can't help feeling that you want another baby because you want someone in your life (not necessarily a baby) - your comment about how you ONLY have your DD 50% of the time and the concern about finding another partner. You need to be really clear about what you want, you may be better off spending you energy (and money) in trying to find a new partner.
in my case when I thought about this - my 2 easy questions were - how am I going to feel if I never have another relationship, how am I going to feel if I never have a baby.
Ask yourself those two questions and see which one feels most scary - thats your answer. If what you want is a relationship (with the chance of more children later) then get yourself down a dataing agency, if its anotehr child you want get yourself down the sperm bank .
Sorry thats slightly flippant but I'm sure you know what I mean.