It's not emotionally or physically healthy to want to have sex with your parent for many reasons this is wrong especially if she is your biological mother. You may be confusing her nurturing you as something a girlfriend does for a boyfriend but that is her natural instinct to nurture her child, you tend to see and believe what you want to see and believe about your mother and the relationship she has with you and in your eyes you see nothing wrong with the way you feel. You are in so deep that what to some would appear toxic and unlawful feelings feels normal to you but isn't normal nor is it healthy and I would suggest getting some counseling for this issues. Regardless of the psychological reasons behind this kind of relationship, in most cases this kind of feeling and wanting to sleep with your mother reinforces the dysfunction of this behavior you feel the urge to sleep with your mother because of fantasy, confusion, guilt projection, double-bind messages which means you mistaken her nurturing for the way a girlfriend feels about a boyfriend. You know this is not how a healthy relationship should be and you don't want to stop feeling this way or even want to make it right. Something about the toxicity of the relationship feels so familiar, even safe in a twisted kind of way. A counselor can help you find out where these feelings came from and how to see that they are wrong and not healthy within the family unit.
It's very important for you to seek some type of counseling to see why it is you continue to test moral boundaries, if you are willing to sleep with your Aunt and now you want to sleep with your mother you need to find out why you only want to sleep with people you are related to instead of finding a girlfriend to whom you are not related. You may have a Sexual Addiction but either way a counselor can help you figure out why it is you choose to only have sexual contact with family member and may be able to help realize that morally and physically this is not healthy. I would suggest you telling the Aunt that you did ejaculated in her because if she gets pregnant that child will have many healthy and mental issues because you crossed blood lines.