I have been dating a nice guy for almost a year, we have great times and great sex. But I'm not sure if I'm in love, that the spark is there. I've been in relationships but I don't think I've ever been in love...
Don't overthink it.
Always remember to come to each relationship and moment cleanly. We tend to bring in our pasts to our futures, thinking that the past is the indicator of the future. This is not true at all. Take each relationship as it's own event and only look at it in the present moment.
You are enjoying time with this person so just enjoy it and see where it goes. Don't put that pressure on the new relationship thinking that you have never had those feelings before and so never will again. Take the days as they come and experience your feelings in the moment. Being in love shouldn't be your goal, be happy, enjoy the great sex and good times and if love is present, then let it develop.
Hope that helps!