what i do, is what i first wake up, before i get out of bed, i start my watch. i sit there and count for a full minute. i don't count for 10 seconds, and then multiple the result by 6. none of that. i don't use a HR monitor or anything.
Boring. Just feel it briefly, you should be able to get a rough idea within a few beats, then just decide if it's regular and feels normal. Job done and you've saved 50 seconds.
Can I repeat: the original poster is by definition experiencing tachycardia but this is not a diagnosis!