From a guy's stand point:

My fiance and I were apart due to work for 4 months. She is a smaller girl and was always really tight. I had to go very slow when we first started dating and then she stretched out and got used to me I guess, but after those four months it almost seemed like we were starting over. I had to go slowly again for the first few times. We just got to see each other again last week and made up for a lot of lost time so we were both sore by the end of the weekend. I'd say just tell him and take it slow.