It just looks like low-quality amateur porn to me. It sounds way too scripted to be ex-gf/bf content, at least in my opinion.
Maybe try to shoot it where she's in the bathroom getting out of the shower or changing or something and you walk in filming. That way you don't start rolling film while she's already sitting half on you and she's like "oh hey I didn't notice that camera" or whatever.
I think you can use a better quality camera too (since you said you're used to them anyway) just skew the lighting all to hell.
The picture you posted looks super natural but at least to me in the beginning of the video it looks like you guys are uncomfortable and are searching for lines.
All in all it's not bad though
