You knew and were smart enough to drop by.
The common wisdom (which I normally take with a grain of salt) says to avoid serious relationships for a year after quitting or more. And that is talking about with sober new folks.
Here you are contemplating going on holiday with a man from your drinking past, and intimate to boot? How senseless does this appear at first glance?
You mention you feel flat and that too is normal. Getting back together with an old flame with alcohol for unflattenning out may be hazardous to your health.
But you knew that.