I know im posting about alot of different topics but im laying here bored and tired sooo.lol :-) but…

I know im posting about alot of different topics but im laying here bored and tired sooo.lol :-) but here go.....my baby boys heartrate has.been in the 150's most of my pregnancy...first one was 147,165 then there after all 150's...my last two were 143 and my last one (last thursday) it was 138...is it normal for the HR to get lower towards the end? just curious...also im meauring 3 weeks ahead as of right now