How can I find out if the process is still ongoing for my security clearance?

Talk to your S-2. They can look up your clearance in a matter of seconds. They will be able to provide your current status and a way forward if need be.

You should have received an email once you submitted the online paperwork to OPM. For reference it can take a year to get the clearance completed for an initial investigation. Most of the time the only update you will get is "packet accepted" until they are going to do your interview.

Your background and social history can play a large role. When I renewed mine in 2014, I had the longest interview of the three times I had been processed and I am sure it had to do with the fact I was married to a foreign national and been all over the globe. One time during a TARP class, I was asked to place all the countries I had been to and a month or so later was called to this building with no windows, no street sign, and interviewed for over an hour. You know your history right now and if you will get the clearance and if you give it some thought, know how long they will dig.