heart palpetations during exercise

When I run my heart, out of no where, will start pounding fast and hard out of my chest for a few seconds and then slow down a little and then it will do it again soon after if I keep up the running. I also get weird heart palpetations after work out sets. For instance today, after I did a set of pull-ups my heart felt like bursting from my chest for a split moment and I took a deep breath and it didn't go any further. I also sometimes get these weird feelings in my chest when I'm just relaxing. I test my blood pressure regularly and is on average 140 over 80, which is a little high. I've been taking a 25mg beta blocker and it is still like this. Im a healthy 23 year old who wants to excell in life and keep fit, but I want to make sure I dont push myself too far and that something serious is not wrong. What do you think is going on and should I be concerned?