ongoing hip 'thing'

A year or so ago I started having periodic hip/leg issues
at the time someone told me it was "hip flexor" muscles and
basically that I was not stretching enough. Off n on this
will flair up on me. Today it is REALLY bad - prob the worst
I have had it and lasting longer than ever before. I am thinking
my walk and short run yesterday morning are the cause. I did not
stretch AT ALL and even though I only ran a short distance I
believe it is the culprit. Dang!
So today, it has bothered me all along... going up stairs has
been pure misery. Trying to lift up my knee is just plain painful.
So I researched it myself and I am going to self diagnose here
and agree with what someone told me originally....

Causes
The most common cause of hip flexor injury is acute trauma. You may experience one specific instance when you felt your hip flexor pull. This may have been when you broke into a sprint, made a cut, or kicked a ball.

Tight muscles and poor flexibility will contribute to hip flexor injury. When muscles are tight, there is an increased amount of tension on the tissues. When this increased tension is added to by an explosive movement, injury can occur.

Hip flexor strain can also be caused by compensation for other injuries, or weakness of other muscles. This is common if you have core weakness. When the lower abdominal muscles do not stabilize the pelvis, the hip flexor muscles will try to compensate for this weakness and become overworked.

***Symptoms***
The most common symptom of a hip flexor strain is pain. It occurs along the front of the hip and may radiate down the front of your thigh. Your pain will increase with movement, especially trying to lift your knee toward your chest.

Running, jumping, and even walking can be painful, and your sports performance may be limited.

The symptoms really cued me in bc that is exactly what I am dealing with.
So now I am on the quest for the best prevention for them... good stretches.
(and a bunch of advil, tylenol and alieve)

Any suggestions??