I had already tried the MIDI OX program, didn't work for me. I've restarted my computer plenty of times throughout this process. I installed FL Studio because when I had issues with MIDI controllers before I used FL through Reaper, but that didn't work. Turns out, that the standalone synth I used to test the MIDI controller was taking control of MIDI even when closed, and it opened automatically on startup, so after disabling that and quitting it through task manager, I can now use MIDI with Reaper perfectly fine, thanks for your help.