Why do I have a sinking feeling in my heart and stomach sometimes?

Me and my girlfriend got into a fight a week ago and we were mad at each other. Now that we are ok I have this sinking feeling like I don't want to talk to her or hang around with her. I know I love her. But this feeling won't go away? What can it be? Plz help.

My mother always says just b/c two people love eachother doesn't mean to be together, ya know?