In the future if I have my own place would a bigger dog even things out since I am big to when cuddeling?

I am thinking a Saint Bernard or English Mastiff would be best for me. My brother is 110 lbs and our dog is 65 and he lays on her and she does not get bothered and I weigh 255 and I am thinking of getting a dog that is like 180lbs to even things out. My brother says I am making our dog uncomfortable and she whines,groans,and barks when I lay on her and hug her but I do that while showing affection and I kiss her snout and forehead and her body. She still lays next to me licks my face and does play with me.I think a Saint Bernard will suit my character because they are not guard dogs and at the same time huge yet still gentle.