I cheated on my gf 3 weeks ago with an ex of mine and I regret it. We were arguing and we weren't talking. Kept texting and trying to talk and was completely shut down. My friend invited me over to his house for a few beers and smoke a bit, and my ex was there (friend told me she'd be there so I wasn't blind sided by it and honestly didn't mind since I wanted to talk about). I wound up walking her home and spending the night. Now my gf is texting me again telling me she's been thinking about me and misses me and idk what to do or tell her or to just day nothing.