Anal play

Hey,

Im 17 and for the first time me and my boyfriend have began exploring anal play.we have been together for 3 years. Rimming and fingering, him doing it to me. Its been very exciting and new for us as in the past we have always disregarded it, always joking about doing it. But recently we have been talking about it more and more. He first lightly played with the outside of it and rimmed me lightly. I really enjoy it and so does he. The other night we where in bed together and we started having sex in the spooning position. He began playing with my asshole lightly circling it. Making me relaxed. And he put the tip of his finger in and then slowly pushing it further inside to half a finger length. It felt really good. Since then we have been talking about it and making sure we are comfortable. Is this bad to do this at this age?