You're definitely not alone in struggling with relapse. I'm there too. It doesn't make you a bad mom and please don't put unrealistic expectations on yourself. Moms have problems and need emotional support too. It's stressful being responsible for someone who depends on you.
You have the strength in you to recover. You just need to find it again. We all three have faded battle scars to prove that we survived and got through this before. I'm here too if you need to talk.