Here's the question as it's stated at the time I'm answering it.
"Am I unscientific, irrational, or cowardly if I am religious?"
While it depends on what you mean by religious, I'll assume (until you correct me) that you define "religious" as believing in god(s) or other supernatural phenomena.
Being Religious is not Unscientific
Believing in the supernatural doesn't make you unscientific. If you study the history and philosophy of science, you'll note that many prominent scientists were religious going back to the classical Greeks and continuing up till today. It's true that the majority of elite scientists today don't believe in anything like a personal god, but the presence of Francis Collins, leader of the Human Genome Project and now Director of the US National Institutes of Health, tells us that you can certainly be a brilliant scientist and also believe in a mainstream religion.
There's a philosophical reason why you can be both religious and scientific, and in fact there's no conflict between these two traits unless you force it. Modern science is defined on the physical domain. It's very powerful at finding out How Things Work, how things in the physical world are connected, what they're made of, and how they influence one another. Science has nothing to say about the metaphysical domain. This is the domain of religion, the domain of What Is and Why Something Is. You probably recognize those questions as being addressed (if not answered) by religion. In fact, the metaphysical domain informs our understanding of science to the extent that we require a metaphysical theory to create a reality (even if it's just a prop) behind our observations of the physical world.
The only time there's a conflict between religion and science is when someone attempts to use one of these outside its proper domain. If a creationist insists that evolution is a lie because that's not how god(s) work, he has (or should have) no standing. Evolution is a widely accepted theory with great explanatory and predictive power. Creationism is an idea of how a god created the universe. Never the twain should meet. Likewise, you find some people attempting to use science to disprove the existence of god(s) or supernatural works. This is futile because the god(s) and works exist in the metaphysical domain, where science is not defined.
Being Religious is not Irrational
Being religious is not irrational, or rather it's no more irrational than many other things humans do. We are raised to prize rationality as a good, unconditionally. We need rationality to survive, and it is a good. But, like science, it's not the summation or the ultimate goal of human existence. Incidentally, the goal of human existence, our reason for being, is another one of those things defined in the metaphysical domain.
Humans are at best incompletely rational and most of us fall far short of full rationality most of the time. While scientists, especially as they are often shown on TV and in movies, are the epitome of rationality, a completely rational person would be incompletely human. Even Mr. Spock from the Original Star Trek was most human and most endearing when his non-rationality shown through. We are all irrational much of the time and that's also a good thing. Many of the best things in life are opaque to rationality. They must be felt in our being.
Being Religious is not Cowardly
I'm guessing you include "cowardly" in your question because you've heard that it takes courage to face the reality that there is no god, no great father to care about you, that nature doesn't care about you, and that life is temporary and death is permanent.
I believe there's no god, nature is impersonal and uncaring, and that death is permanent, but it's not because I'm courageous. I just couldn't accept the god(s) of any religions as being real, and I've studied religion and philosophy for a long time. I don't think it's cowardly to want to believe in a heavenly father that cares for you now and will ensure death is only temporary. It's very human and I'd like to believe that myself. I just can't.
I hope this is helpful. Please tell me if this makes sense and where it's unclear. I've tried to avoid jargon and keep things at a layman's level and I may have overly complicated things or made them unclear as a result. I can certainly go back and clarify where necessary.