Feeling movement from the outside

Kayleigh • I`m Kayleigh, 26 from England. With my SO 5 years & engaged 1 year. Just brought our first home and Pregnant with #1
I'm 19 weeks today. When I feel baby move on the inside I put my hand on my belly and all I can feel is a constant pulse from the outside.
I was just wondering if this is what other people have felt? If not I was wondering if it the placenta pulse I can feel. Apart from being told at a scan is there any other way I could tell that I have an anterior placenta? 
Thank you