Complicated relationships

So way back on February 15, me and my boyfriend got into an argument that left me thinking we'd broken up so that's what I told my mom. But it turned out that it was just like one of our usual arguments where we fight and make up (we don't often argue, don't worry). I'm still with him but my mom thinks we're broken up and I don't want to tell her that bc she doesn't really like him (bc he's really sexual and she knows that; he doesn't use me for sex at all; he knows the difference between yes, no, stop, etc) and it'll make me and my mom's relationship shaky bc she won't trust me. What do I do?