Good advice from Getvertical_PV!
Take advantage of this site!!! The pole vault is TECHNIQUE TECHNIQUE TECHNIQUE!!! You'll find the confidence, motivation and joy for the sport again, just give it some time. For beginners and intermediates, sometimes the bar height is not always an indicator that your getting better as a vaulter. As coaches we like to put a bar up early in the learning phase, this creates an interest and sense of accomplishment but more importantly will determine if the athlete likes the sport. The next step is laying down a good foundation: proper pole carry,run technique and posture and a perfect plant. It's these very important foundation fundamentals that sometimes loose our vaulters interest because we not jumping over more bars! more PR's! When we are first exposed to high school track and field our coaches are pulling us all around the track to see what event is a good fit. You may want to PV but the distance coach may want to put you in the mile(had to put that in there !)

, We as coaches may not want to lose you so we put the bar up to kept the interest going. Without a solid foundation that bar will only go so high before we plateau. Pole vaulting can have a lot of mental and emotional peaks and valleys at ANY level. I would bet your not at one of these valleys but you may feel you are! Work on the little things! THE most important things in the vault are all the little, but essential things BEFORE you leave the ground! When I was in high school this was a tough pill to swallow and later in life would regret for not believing. Without a description or video of your vault one could only guess why you may be in a rut, my guess it's roots, like most every vaulter, are before you leave the ground. The best thing to do is post a video clip of your jumping on this site. Video your whole jump, run and all, preferably a side shot from your take off point. After you post your video, don't be overwhelmed by the responses. Take one aspect of advice at at time. Be open minded to critique. Some advice you receive on this site(PVP) you can change and benefit as soon as you step on the runway, some things will of course take longer...this is life!!! The pole vault will be one of the hardest and most technical things you'll do in life and you will be glad you did it later in life. Once you start putting the puzzle pieces together(in the right place:) ), your PR's will start coming again!
The internet is a great tool to learn anything, something I never had when I was jumping. PVP can be a godsend for vaulters that want to learn, please take advantage of it!
Good luck!