Hi!
When approaching a model like this, it is important to break it down to simple geometric shapes. The design, from what I can see (this reference isn't really good) is basically 5 overlapping cylinders with slighty eliptical top faces. One of which is flattend where the bottle neck is.
Create those objects, position them right, delete everything you dont need and connect the rest. Then you are basically done.
It also helps to create good reference images. Use a lens with a High Focal Length (50+), make sure you are really getting your objects from straight from the front,side, back, and top not slightly slanted like the attached image... I normally also make a reference for the bottom and 4 references for the three-quarter inbetween angles of the object. Being prepared makes modelling easy.
I had 20 minutes on my hands so I modeled the body of the bottle. I'm assuming that this is the part you are struggling with, since it is the only thing I can really make out in your reference. It's not perfect but maybe something you can build on.
Have a nice day!
