Need Help

I desperately need advice. I have a horrible habit of accidentally ghosting people for a reason that I just can't figure out. I recently got a girlfriend, and overall it's been going pretty well. But one day I just didn't respond to her. We haven't spoken in a little over a month. I want to talk to her again, but I just don't know what to say. I don't know how to explain why I haven't talked to her, especially when I don't even know myself. I know it's wrong but I'm not above lying, honestly. I just need advice on anything I could say to apologize and let her know I truly do care about her, anything I could possibly do to make it up to her. Thanks for reading.