Is he just fulfilling a fantasy?

I female (28) have been dating a male (25) for the last month or so. We both used to work with each other 6 years ago and he has openly said he used to fantasise about me back then and I’m worried that he’s using me to fulfil a teenage fantasy.

We have met up a number of times and both seem to enjoy each other’s company. As things have progressing we agreed to not have sex until we were both sure the relationship was heading in the right way and we were both sure.

Things have happened in between, he has given me oral and things were fine afterwards.

He made a pledge to remain celibate for a period of time for self control and clarity for 20 days. Today was the 20th day and I decided to give him a blowjob, immediately after he seemed off and distant. He didn’t give me any affection and I felt as though he was acting weird towards me. I asked him to be honest with his feelings and he said he felt no different and that he was happy to see how things went and if his feelings towards me changed he would let me know. He said he wouldn’t try to force anything and let things flow naturally.

Prior to the blowjob we were cuddling and he was stroking my legs, however after, there was nothing. Just a hug and a kiss before I left.

In my gut I feel as though he’s acting different and I’m unsure how to process this. When he’s horny he wants to talk a lot but after this instance he’s avoiding discussing it. He did message me once I had left to tell me he enjoyed my company and to let me know when I was home.

We speak on text everyday and we used to have deep conversations over text in the evenings every other night but this seems to be non existent now.

Please could someone help me understand this situation because it is really making me uneasy.