My boyfriend and I just started saying I love you ands ex has changed?!

My boyfriend and I were FWB and we grew to being into boyfriend and girlfriend we are in love I love him with all my heart but it's crazy to me that our sex has changed. We use to have hardcore sex. I loved it now it's all slow sex I try to go faster when I'm on top but my boyfriend slows me down and says it's more meaningful. What the hell?