Moms home is in my name. Medicaid 5 yr look period is up 5/20. Can I put it on the market in 6/20?

Five years, you are good, but I would check and see exactly when the county indicated title was transferred.  You may have sent papers to attorney and/or county, but check when recorded. 

Yes, that's what struck me - the question seems a bit back to front. Your mother's house was transferred to you in 2015, then. So from May, it will not be included in Medicaid's assessment of your mother's property.

I hope you don't mean that your mother transferred the house to you in 2015, applied for Medicaid and was accepted, and kept shtum about the house - not disclosing it to Medicaid on the grounds that it was in your name.

Is your mother already in receipt of Medicaid? Where is she living?

I mean, you can sell her house for her any time you like if she isn't going to live in it again; the only question is what happens to the proceeds. But as I understand it, if she moved permanently out of her house as a Medicaid recipient but had owned the house within the look-back period, there should have been a lien put on the house to reimburse Medicaid after its sale. No?

There are forum members who really do understand these processes: if you could provide a timeline of what happened when I'm sure they'll be able to guide you.

It probably depends on how long the house has actually been in your name as compared to when Medicaid was applied for. I think that's the issue you're facing and an elder law attorney will know and it would be worth the legal fee to find out. In general, the longer the house has been legally in your name (5+ yrs), the better off you (and your mom's Medicaid) will be if you sell it. You seem well aware of when the lookback period ends, but please make sure your dates match the dates Medicaid is using. I once had someone offer to "sign over" their house to my name if I would only just clear up the itty-bitty lien on the property - which ate up almost half of the home's value. I refused to do this. Good thing I refused because the owner soon went to a nursing home and applied for Medicaid. The house was sold, the lien was paid, and the rest went to the nursing home. Not sure if my interests would have been protected in any way if I had paid that lien because it was less than 5 yrs that the house would have been "mine." Glad I didn't have to find out. Not sure what owner was trying to accomplish by having me pay her lien, but I was sensing a scam in progress.

I would wait a bit anyway. 3-6 months. But, get with that elder law attorney.

I’ll respond to keep your question more visible.
Can you? Probably could have five years ago. Should you is probably what you mean without jeopardizing your mom’s ability to receive Medicaid. I assume you don’t want to jeopradize that or you wouldn’t be asking. I think the five years look back begins from the date she applies for Medicaid. If it were me, given the cost of NHs, I would be speaking to my mom’s certified elder attorney to make sure. You could possibly put it on the market earlier with a provision that it couldn't close before a specific date. That date being the one when she is able to file without fear of being rejected due to the five years.
Sorry I’m not more helpful.