I agree with SU on what your 3:50 would indicate. However, if you haven't done anything much faster than 2:55/800 pace in the last several weeks, you may find that the *skill* of running at a sustained ~80/400 pace is lacking. However, that skill will return very fast, typically with just another race or two (or three).
The first race of the season can be frustrating: you hit the finish line (perhaps with a somewhat disappointing time) and two minutes later, you're completely recovered and really kicking yourself for not having pushed harder in the race. No--you pushed as hard as you could; you just didn't have the racing sharpness yet to get everything out of yourself. It's paradoxical, but you have to have really great racing fitness to be truly exhausted when you hit the finish line!