NO omg

What do you mean when you say OMG?  Most people say it means "Oh, my god" , or "Oh my God" or "oh my gosh" or "oh my goodness."  What do you mean when you say it?

So, your defense is that you're not saying "oh, the real, god..." but instead "oh MY OWN god."  That's no better than blasphemy.  If you're admitting to having your own false god, that's breaking another of God's 10 Commandments.  Read for yourself: "I am the Lord your God… You shall have no other gods before me" (See Exodus 20:2,3)

So you say you don't believe in God.  Then why do you use His name to cuss?  Do you use the name's of any other people who you don't believe in to cuss?  Besides, if I stood out on a freeway and told you that I don't believe in trucks, would that make much of a difference to my safety?  Nope.  And you are also in danger if you are breaking God's Laws... the fact that you say you don't believe in Him is just adding to your sin.  In addition, it's likely breaking the ninth commandment (you shall not lie) -- because more than likely you do believe in God, you just may not like Him (because you don't know or understand his goodness).

"Thou shalt not take the name of the LORD thy God in vain; for the LORD will not hold him guiltless that taketh his name in vain" (Exodus 20:7)

Here's all ten commandments, straight from the Bible:

And God spoke all these words, saying, "I am the Lord your God, who brought you out of the land of Egypt, out of the house of slavery. "You shall have no other gods before me. "You shall not make for yourself a carved image, or any likeness of anything that is in heaven above, or that is in the earth beneath, or that is in the water under the earth.5 You shall not bow down to them or serve them, for I the Lord your God am a jealous God, visiting the iniquity of the fathers on the children to the third and the fourth generation of those who hate me,6 but showing steadfast love to thousands of those who love me and keep my commandments. "You shall not take the name of the Lord your God in vain, for the Lord will not hold him guiltless who takes his name in vain. "Remember the Sabbath day, to keep it holy.9 Six days you shall labor, and do all your work,10 but the seventh day is a Sabbath to the Lord your God. On it you shall not do any work, you, or your son, or your daughter, your male servant, or your female servant, or your livestock, or the sojourner who is within your gates.11 For in six days the Lord made heaven and earth, the sea, and all that is in them, and rested on the seventh day. Therefore the Lord blessed the Sabbath day and made it holy. "Honor your father and your mother, that your days may be long in the land that the Lord your God is giving you. "You shall not murder. "You shall not commit adultery. "You shall not steal. "You shall not bear false witness against your neighbor. "You shall not covet your neighbor's house; you shall not covet your neighbor's wife, or his male servant, or his female servant, or his ox, or his donkey, or anything that is your neighbor's."

Exodus 20:1-17 ESV

Blasphemy is speaking evil of God or denying Him some good which we should attribute to Him.  It could also be understood to be acting in any impious, mocking or contemptuous way toward any member of the Trinity.1 The word blasphemy comes from the Greek word , blasphemia, meaning "curse" or "vilifying." 2 Blasphemy arises out of pride (Psalm 73:9,11), hatred (Psalm 74:18), injustice (Isaiah 52:5), etc.  Christ was often mistakenly accused of blasphemy by Jewish leaders (John 10:30-33).