Depression can make you feel more self absorbed, but I don't think it can make you stop loving someone.
Severe depression has taken away just about everything in my life, but the only thing it has not been able to touch is the love I feel for my wife and family. It can kill everything else, but for some reason it doesn't seem to be able to kill your ability to love.
Depression can make you feel like you don't care about anything or anyone. Your medication can take 2-4 weeks before it helps you feel better, and even then they sometimes have to up the dosage. Sometimes we do fall out of love with the most wonderful people, and you can't make these feelings happen. They are either there, or not. My daughter married the most wonderful man, who was such a good person and husband. But after about 2 years, she didn't feel she loved him like he deserved to be loved. It broke her heart (and ours) to have to leave him, and she cried so much over it, but had to do what was best for the 2 of them. I even sat with him and we cried together. He was everything a mother would want her daughter to have in a husband, but it was her life, and I respected that she didn't want to lead him on. So, back to your question. Yes, you can feel like you don't care about her, but this shouldn't last after you have been on medication long enough to not be feeling the depression. At this point we tend to see who has stood by us, and who has not, and gain a new appreciation for a girlfriend, boyfriend, spouse, etc. A lot depends on how long you've been on medication, and if you are no lomger feeling depressed, you may have to accept that you no longer love this woman. She may be the most wonderful, and amazing person, but it's either there or it isn't. Good luck to you in all this, and always remember that everything happens for a reason.