Outerwear is made with special fabric, and so it requires special care. If you take care of it, it will last longer and work better. Here's what you do:
Go to your local outdoors/ski shop and get the care products you need. Personally, I like Nikwax, so that's what I'll suggest.
First, use Tech Wash
(or something similar) to clean the jacket. Traditional fabric detergents clog the pores that let your jacket breathe, so unless your girlfriend likes you sweaty and stinky, use the Tech Wash.
After that, you need to redo the waterproofing. Jackets are built with a number of layers to the shell fabric, but they all have a DWR (durable water repellent) finish coating to stop water before it even hits the fabric. DWR works like a bunch of little umbrellas, and normal wear and tear scrapes them off the fabric and dents them in.
To redo and rewaterproof your jacket, pull it from the washer, still wet, and spray it with a heavy coat of the TX Direct
They make wash-in waterproofing too, but it coats both sides of the fabric and messes up the lining, so get the spray on.
After you've coated it, throw it in the dryer. When you take it out, it'll be clean, more waterproof, and you'll be happy.
It's best to wash multiple garments together. If you can't afford it yourself (about $30ish for the Tech wash and TX Direct), go together with your friends and take care of all your gear.