Masturbation is an act of self pleasure. The bible tells us to please God not ourselves. ( 1Th 4:1 Furthermore then we beseech you, brethren, and exhort [you] by the Lord Jesus, that as ye have received of us how ye ought to walk and to please God, [so] ye would abound more and more. ) Sex inside a marriage is so he will please her and she will please him and in so doing give completely of yourself to your spouse. This is not saying that anything in the marriage bed together is wrong, just if your spouse is not there then you should abstain until his/her return. Learn to please your spouse just to please them as you are so willing to please God, and not be selfish in the doing as this glorifies God and He will bless it. Yes, God blesses sex in the marriage bed as He made sex to be enjoyed and to draw the two into oneness.