"I'm just wondering if there are any other ways of going about this"

You mean the magic way that makes your ex have a miscarriage and keeps your girlfriend from finding out?

Are you really being serious now?

Your dick didn't accidentally end up inside your ex after you slipped on a banana peel. You had sexual conversations with her and then got in your car and went to see her. Oh, and you somehow forgot to mention to your ex that you have a girlfriend.

You're 35. Be a grown up and tell your current girlfriend that you betrayed her and let her dump you.

Then you need to stop dating while you get some therapy and focus on being a dad. You need to expect more from yourself, especially at your age. Cause right now, you are an embarrassment.