Please get some sleep,

I know nightmares are terrible, but if you don't at least sleep a little bit at night, you'll suffer their effects during the daytime as well because of the insomnia they're causing you.

You are waking up at 3:30 for a few reasons off the top of my head:

a) REM sleep is the stage of sleep where dreams (and unfortunately for you, nightmares) generally occur. These stages become progressively longer as the night goes on, and therefore the chance of getting a nightmare also goes up. This is why you are suffering from nightmares so early in the morning.

b) Your circadian rythms can be very specific. If you are constantly waking up at the same time, your cycles will reset at the same time too, so you will enter long phases of REM sleep at the same times as before.

c) If you are taking ANY drugs which act on neurotransmitters, such as anti-depressants, mood stabalizers like lithium, or illicit drugs like cocaine, these can actually be the source of a high frequency of nightmares. Other drugs, in a few people, can increase nightmares as well.

Solutions:

a) You need REM sleep -- all mammals do. There is nothing you can do to escape them: In laboratory studies animals eventually collapse from exhaustion or die when allowed to sleep, but not allowed to enter REM sleep.

It is essential for your brain's health.

Eventually you WILL fall asleep -- but it could be behind the wheel of a car or down some stairs. You could actually hurt yourself and/or others.

b) Keep taking any medications, but talk to your doctor/pharmacist about changing it if they believe it could be causing your nightmares.

c) Try going back to sleep immediately after you wake up from a nightmare. This will prevent your circadian rythm from repeating the pattern and causing you to have a high probability of getting a nightmare at 3:30am.

MOST IMPORTANTLY:

See a doctor or qualified psychologist.

Post Traumatic Stress Disorder can commonly cause chronic, reoccurent nightmares. Major depressive disorder, or high anxiety (or an anxiety disorder) are also likely culprits.

It is actually normal you don't remember your nightmares. Generally people just wake up feeling extremely anxious and/or terrified

Just remember you have nothing to fear but fear itself. You cannot die from a dream, or become harmed from it in any physical way other than sleep deprivation. You will be okay, and you'll get past your nightmares so they never bother you again once you and a doctor/psychologist figure out the exact cause.