heart rate while running

Hi everyone, just have a question, I recently starting running again as I want to try and run a 5K. On average I have been running about 2.66 miles within about 35 minutes at approximately 13 minutes a mile. I can't run the full thing. I start walking then jog some then walk, etc. I have been trying to push myself between every other light pole, lol. I walk at an average speed and feel I jog on a slower. For the most part, I will jog until I struggle with breathing then will walk until I catch my breath. I wear a Sportline heart rate monitor and noticed it was reading 180 something and my percentage was marked high so I would walk until heart rate went down to 170 something. So, my question is if Im already jogging on a slower pace and have to stop and walk alot, how to I increase everything and be able to run longer without stopping and keeping my heart rate under 180?