even if you're not seeing a large change in your weight you said you're seeing an increases stamina and endurance and that's great! Unfortunately plateaus happen and they can be very frustrating. there's a few things you could do if you're concerned you can try carb cycling, changing your metabolism by overloading your calories one day and then under loading them others to see if you can ramp up the metabolism speed, you can increase your exercise output a decrease your calorie input. or of course you could just wait it out and see if it's just a temporary lull. Regardless of what you choose to do it sounds like you're at least seeing nice gains off the scale and sometimes non scale victories are just as nice.