Not everyone is into rougher breast play, but some people are! You are experiencing positive sexual touch, mk? There's even some evidence to suggest that a few lucky folks can.
You can increase sensation as you move along and they become more aroused.
And this is assuming that your partner wants you to play with their breasts at all—many people with boobs do not, particularly if they're breastfeeding.
I am having a great time, too.
So you probably want to know how to play with them in a way that's pleasurable for both you and your partner.