Feeling Lonely

Hi, I truly feel like I have lost myself after 17 years of being a parent to 3 kids. I know it’s still all about them and with 3 kids who play sports it’s busy but I really feel lost. They have their social lives and are growing up which is all good and normal but in the process my husband and I have lost friends due to our kids not being friends anymore or just not being able to go out because we didn’t want to leave our younger ones alone. Now that the kids are 12, 13 and 17 we shouldn’t feel this way anymore. But yet I’m so used to being a certain way whenever I’m about to make plans like go out to dinner with another couple I get worried and don’t go. I even worry about leaving our puppy alone. So there’s always an excuse to not do anything fun for myself or with my spouse and now I’m really starting to feel overwhelmed and confused on what I even want to do and who we even want to spend time with. So I often feel lonely and bored especially on the weekends. Any suggestions how to get my life back and not feel like at 50 my best years are all behind me?