Alright, I hate to also be the bearer of bad news, but it's best to throw it out there so that you don't miss it and deal with the injury longer, like I did lol I had the same symptoms for over a year until it royally blew up and left me unable to walk normally, let alone run. I'll give you a few things to try that bothered me when other things were totally fine. Lie on your side (the same side as the "bad" hip) and do a leg raise with the affected leg (so as to use the adductor to lift it towards the ceiling) opposite of a normal side raise. That killed me. Also, if you have a friend that can assist get in the same position (this will be done on both sides) and do a normal side raise and hold it, now have your friend apply pressure and you resist it. See how that feels. I've extensively researched everything that involves the hip, nerves, the back, etc. The issues associated with what can be mistaken as a groin strain are compression of the obtorator nerve via inflammation of the psoas or surrounding structures. I too would have days, weeks, and sometimes months of relief with slight "pressure" deep in the groin. I truly hope this isn't the issue you're having, but if it is I'd meet with an ortho to get an MRI. You'll need an arthrogram which is a dye injection to ever even see a tear, but you'll figure out whatever the problem is via MRI. Obviously this is pretty much if things get unbearable and you've exhausted all other resources.
Some things to keep an eye on: If you feel shooting pain into your lower back on one side (check out hip spine syndrome)
Shooting or dull pain up buttcrack region
Numbness in genital region,
weakness, clicking, or giving out during activity
Pain, numbness, weakness in the front of the thigh/IT band area that stops at the knee
The reason I was able to have periods of relief was due to the fact that there are limited nerves in the hip joint capsule itself, thus limited pain receptors. So, when the inflammatory response would be triggered it would take time for the mediators to get out of the capsule.....the problem with the hip is that it is a close neighbor to a heavily innervated area that will pick up those mediators and cause pain all over.
I spent a year of running on it and it never got better, and I wish I knew what I know now haha After seeing multiple doctors I wasn't able to get any answers, so I saw an ortho that specialized in this type of thing by recommendation by a sports massage therapist. There are only 4 doctors that do hip arthroscopy in my state, so you may have difficulty finding someone that could diagnose it if that's your problem...so be weary of who you work with. MRI's can be expensive and you need a specific one to see a tear, or you'll miss it and waste money.
Good luck, I hope it's just a strain