Tempo Run??

First time try the tempo run. I am not sure if I am doing it correctly but I ran for 5 minutes with slow pace (my normal long run pace for around 0.5km) and speed up at higher pace for ~10 minutes (1.5km). I then continue with easy run for another 2km. However, I felt very tired and a bit of muscle discomfort after the run. My initial target is to run have 5 minutes easy run follow by 15 minutes of fast run and then another 5 minutes of easy run. Seems to be too tired for me to run for 15 minutes at faster pace. Hope I can improve it my timing/distant in tempo run next week.