What does your contract say? Did you sign a buyer agency agreement? If not, you can use whoever you want to buy. If your home isn't even listed yet, or not under contract, it doesn't make sense to look at homes if you can't put an offer on something. You posted under zip code 80127, which is Littleton CO (and a very HOT market). It's very hard to get an offer accepted with a contingency to sell your current home. If you're under contract, and very close to closing, then I would demand to look at homes at this point.
I have potential clients asking to look at homes, but they need to sell their house first and it's not even near ready to list. It makes zero sense to look at a home, fall in love with it, and then not be able to make an offer on it.