If all the prophecies about Christ were not fulfilled by Christ, then every "jot and tittle" of the law is still in effect today and the man known as Jesus was not the Christ.
That is not the easiest passage to understand so let's put it in context and take a closer look, shall we?
Matthew 5:16-22
16 Let your light so shine before men, that they may see your good works, and glorify your Father which is in heaven.
17 Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfil.
18 For verily I say unto you, Till heaven and earth pass, one jot or one tittle shall in no wise pass from the law, till all be fulfilled.
19 Whosoever therefore shall break one of these least commandments, and shall teach men so, he shall be called the least in the kingdom of heaven: but whosoever shall do and teach them, the same shall be called great in the kingdom of heaven.
20 For I say unto you, That except your righteousness shall exceed the righteousness of the scribes and Pharisees, ye shall in no case enter into the kingdom of heaven.
21 Ye have heard that it was said of them of old time, Thou shalt not kill; and whosoever shall kill shall be in danger of the judgment:
22 But I say unto you, That whosoever is angry with his brother without a cause shall be in danger of the judgment: and whosoever shall say to his brother, Raca, shall be in danger of the council: but whosoever shall say, Thou fool, shall be in danger of hell fire.../
Now right off the bat before He says what you quoted He says let your light shine before men...
That does not sound like someone who does not follow the law but does follow it and behaves themself and not lying or committing adultery etc.,
Then He says that He has not come to destroy the Law or the Prophets, but to fulfill them...
He's talking about fulfilling the Law by being sinless, and then giving His life and blood as payment for man's sin.
Then He goes on in v18...for truely I say to you, Till heaven and earth pass, one jot or one tittle shall in no wise pass from the law, till
all has been fulfilled...
Has heaven and earth passed away yet? Does "until ALL has been fulfilled" mean the same thing as "the Law and the Prophets" being fulfilled by Jesus? No. There is more to be fullfilled yet, so the Law IS still in effect. He is talking about two different things and goes on to clarify what He means in verses 19-22 so there is no confusion. You better not break even the least of the commandments or risk being called least in heaven. And your righteousness better be more than the Pharisees was (and He called them vipers and hypocrites!). In fact you better not even call someone names or a fool or you may find yourself in danger of the council or even hell fire! (Or even look at a woman in lust!)
So...no Brother. You misunderstood that passage. We are not dead to the Law. We can't go out chasing girls or wot-not. I suggest studying the entire chapter of Matthew 5 because He really is very clear about it.