Heart beat

Hi. I have a problem with the heartbeat. It seems to stop my heart as if a beating is not done or it seems like a have a space between 2 beats. It lasts for 30 minutes. It becomes more frequent before and at the end of the menstrual cycle. When I get nervous, when I get bored and when i stay in bad straight.sometimes it happens when i breath with mouth.I'm 35. I'm anxious for this. I do not understand what I have It beggin during the supper and it was only in night. Now it happens every time. Or it happens when i move quickly i feel something different to.me