Antifreeze on driver side floorboard

Over the winter my heater stopped working and a local
shop told me I had a partially clogged heater and it would
cost me almost 2k to get it fixed. I decided not to get it
fixed. About a month ago I was driving to work and
noticed my car was overheating. Luckily I was close to
another local shop so I drove it there. They ran a pressure
test over night to try and find the leak but they couldn’t.
However, since then I have to add additional coolant
about once every 7-10 days. Within the past week I’ve
noticed that my driver side floorboard is sopping wet
which thinking back on it has probably been going on for
a couple of weeks. Now I’m debating on trying that blue
devil head gasket sealer stuff or do I need to just pony up
the cash to get the heater core and the leak fixed by a
professional? Or can I just live with the leak and keep
adding fluid or is that just a bad idea?
I should mention that my car has 165k miles on it and I
just dropped about $1500 on it to get an oxygen sensor
fixed. I think the car is now worth only about $7k if it was
in good shape. Any thoughts or advice would be greatly
appreciated! Thanks in advance.