Leaking coolant

I had two antifreeze leaks. Got the radiator hose replaced on the passenger front now I am leaking and losing coolant on the driver front. I can see underneath my truck where it's leaking down on because certain spots is wet and the antifreeze can be seen on the ground plus I can hear liquid sloshing around when I drive sometimes. Before I got the hose replaced I was leaking and I was putting antifreeze in like every week but still had some in the reservoir but since the radiator hose was replaced. I'm losing antifreeze big time going through at least two gallons a week.I can fill it up and about time I make it back home, it is back empty. I am lost at this point. Please tell me what should I do. Also, I did have a used engine put in back in 2017. So do you think that it's the used motor. But i've had my truck for nine years and this is the first time I started having coolant leaking problems. Do you think it's the hoses? Once I got the one on the right side replaced I haven't had any leaks out of that one.