Sounds like you need to get faster. Strengthen your entire kinetic chain through strength training and sprints. Strength training also helps with injury prevention if you do it right, but most people do it wrong. Don't be one of those.
Doing it right:
Do around 3 core compounded strength training exercises: a triple extension (e.g., snatches or deadlifts), a squat variation, and an upper body lift. Ideally, you'll have alternatives for each that you'll cycle through every so many weeks.
Sprints. A lot of up hill running, or running in soft grassy fields.
*** I'd also recommend some loaded carries, going heavy sometimes, going light for instance other times. Some might poo poo this idea, saying that time under tension doing heavy loaded carries will put you over the edge on muscle growth. However, if you run a lot you'll have trouble adding much muscle (especially if you're a woman).
I'm also a proponent of running less by doing more cross training. I get injured at my age with much volume, so I do a lot of low impact cross training for most of my steady state stuff.
This kind of program won't make you elite, but it will make you faster, stronger, and more well-rounded. Your marathon time will suffer though. (I don't care, do you?)
When you say “get faster and stronger” I assume you are referring to my top end speed and strength in the sprints. What sort of 100m/400m times are required to go sub 20?