Ugh I messed up

So long story short, I'm an idiot and need advice from you lovely ladies. My ex and I recently broke up and for awhile, up until this past week when I decided it was time to move on and end contact, I've been super hung up on him which is understandable all things considering, buuuuuut I feel like I messed up. A co-worker of mine has been flirting with me and going out of his way to compliment me and help me at work. At first I was so hung up on my ex that when he suggested hanging out I said no. OOPS MISTAKE. My coworker is actually a really great guy, I'm attracted to both his physical attributes and his personality. But I feel like I messed up when I said no the first couple of times he suggested it. He still flirts with me the same amount if not more, I just don't know how to go about making it obvious I want to hang out considering he hasn't actually asked again in a couple of weeks since I first said no. HELP ME. What would you ladies say/do?