The female breast is a part of a woman’s body that is often used during sexual relations within a marriage, then after birth it is suddenly part of very intimate motherhood. That can be a very difficult switch to make in your mind-set. I would try closing your eyes and inviting the Holy Spirit into your heart and mind for prayer before each nursing session.
It is not unusual for a newly nursing mother to suddenly have unexpected and unwanted sexual feelings of arousal. This can be highly disturbing as you can imagine. It can make for guilty and awful feelings. Some women are afraid to talk about this because it is embarrassing and they are afraid people will think they are nursing because it is a turn-on. In fact the reaction usually only lasts a few seconds but is enough to turn the stomach of most women because they are trying to bond with their baby.
One idea is to take the “feeling” and recognize that it is simply the bodies physical and momentary reaction. Do your best to accept that fact and that the feeling is temporary and it will pass. Ask God to help you through the feelings of awkwardness for the sake of your baby and for the grace to get through it so you can give your baby the gift of nutrition and love.