Early Labor

So yesterday around 10:30am I went into Labor & Delivery and stayed their until 2:00 pm when I got released. I was 3cm when I got there and I was told to walk and I ended up getting to 4cm within an hour. I was sent home because I stayed at 4cm for another hour and half & that my contractions weren’t close enough and random. Nurse told me I was in early labor. Do anyone know how long you can be in early labor before you go into active labor? I’m currently

38 +3