Constant Palpitations Due To Use Of Nicotine

Hi, I m 23 and I m having constant palpitations for a while now but I always blamed stress and nicotine for it, I m also noticing PVCs quite frequently lately . It s not interfering with my every day life except when I lie down to get some sleep, it seems to get worse than. I m not sure if it s subjective perception or the symptoms really get worse. At night I would get couple of skipped beats per minute when it s really bad. I m otherwise healthy and walk a mile per day at least to get to my university with no problems, even 300 stairs that I have to overcome are no problem and I do it while eating. My BP is 120/80 and resting pulse is around 70-75 usually, have no fever , no splinter hemorrhages or anything else that would suggest an endocarditis . I did however had a heart murmur as a baby, but it went away, probably patent foramen ovale . I find no cause to my problem, despite studying medicine everyday, so yeah... I m pretty frustrated and stressed out. Please help