I'm a pathetic cheater..?

I cheated on my ex after a multiyear relationship and continued the new relationship for a few months. I have done my part to make amends and convince her I am serious about renewing our relations. I am willing to go to relational therapy and everything else it will take. I realize I am powerless and I have made my sincerest apologies. For anyone who has been here, and trust has been lost, yet it can potentially be EARNED BACK, I need personal expiriences and advice. We have been texting and emailing for about two months. We just started to see each other and talk on the phone. I know it will be a long recovery if it does work. The issue is the ups and downs. One minute she is happy, the next she is down. One minute she wants to see me, the next she says we shouldn't talk again. It is continuously like this. I know I can walk away and start fresh, but we do have something special! I want this. How do I deal with these ups and downs? Are they common? She texted me I will miss you :(, what does that mean? Isn't the frowny face signifying she isn't happy about moving forward without me? ANY HELPFUL INPUT WILL BE GREAT!