I told him I wanted him back

Me and my ex broke up... 130 days ago basically(remember the day) when we broke up, we still talked, but didn't see each other for a month. But I was "in a relationship" and he was "talking to someone" but said it wasn't serious. I broke up with him, but I regretted it. We been hanging out for a month or two, and I actually felt like I was falling back in love with him. I got to see who he was without all the tension. We dated for 3.5 years but we were immature, so I told him I basically wanted to start over, that I still love him, miss him, care about him. And he said the same thing, and we talked it out.  I'm just scared and don't know how to START OVER. But I'm so happy he feels the same way and so GRATEFUL he wants to start again.