Can I modify our visitation order for extra time?

I have a 4yr old son.i took her 2 court 1.5 yrs ago bcoz' she denied access 2 him when i came back 4rm bootcamp. They decided residency w/ her becoz' I was gone for 6m. i have him wed @ 9 2 thurs @ 9 every week and fri @ 3p till Mon @ 9a every other week, w/ joint custody. me n my son have a very strong bond and he has a 1yr old bro (from my wife) that looks up 2him. His brother is very affectionate 2 him when he comes home, just the sight of him or even a pic gets his little brother really happy. When we made the order it seemed like i had him plenty of the time but after a year and a half.. its not enough. I wnt the kids to spend more time together and I want more time. I am married and she is a wonderful stepmother 2 my son, she takes him in like her own. The mothr of my 4 yr old can b difficult 2deal with. otherwise we could of worked this out out of court. I do pay child support. I am a VERY loving father to my son, i technically cared 4 him his first 1.5year of his life so his mother can party, To cut the story short, i've gone through ALOT with this female, ive tried to do civil to be respectable parents but in her eyes there NEEDS to be "bbymama drama", i AM NOT SUGAR COATING THE LOVE AND CARE I HAVE FOR MY SON, I am not a felon nor a drug user. oh, we both live in El CAJON, CA 7 min away from eachother and his school is closer to me because im the one that enrolled him. when he is not w/ me he is overnighted with his grandparents half the week. hard to prove.