I used to have a main drain line that clogged every other month or so, and I would fix it by running a stiff garden house down the clean out before the clog with a metal firehose type nozzle on it. I would run it down until I hit the clog, then turn on the hose and push and pull it until the clog cleared.

However, your main drain line clogging constantly is an indicator of a larger problem - it is wider than your house drains so it’s likely there is a problem in the drain line that needs to be addressed. In my case, a tree root had entered the main line and it was about 75% blocked. I had to have that section of the line replaced. I tell you this because in the long run it might be necessary to have a professional diagnose the issue. See if a plumber would just come to run a camera through your drain and diagnose the problem. They might also apply that fee to the cost of a water jet or auger clean out if you decide to do it. I understand money might be tight but this may not be a DIY job.