My car I slosing coolant

My car I slosing coolant. I travel approx 35 miles to work and back. The coolant light comes on in the morning as I reverse from the drive. I top up, and drive with no problems. I get in the car 6 hours later, as soon as I set off the coloant light comes on, and resovior is very low. Ive been doing this daily now for approx 2 weeks. The car has been pressured up with a machanic and no leaks detected. I was however able to collect some (not a lot) water with anitfreeze by placing a roasting tin underneath the drivers side when left overnight. For this reason, it was assumed it was the water pump, and this was replaced. Car ran fine for a day, then problem occured again. The whole system has been flushed at least 3 times. Ive laso had a sealant added to the radiator incase of pinholes. Im not showing the typical signs of blown head gasket, except a slight misfire when engine is cold, but this has been there for months. I can smell coolant through my heaters as car warms up too.
Oh, and when it first started, my temp was running up to 130, then back to 90, so the thermo was also changed. Temp gauge has been fine since, but im still slosing collant somewhere. Please help!