You have a good problem on your hands; you're growing. Lots of startup founders wish they could be where you are right now, so give yourself a pat on the back! Way to go!
Now, you need a way to generate revenues quick or raise some capital or you might be brought down by your growth. I would ignore angel investors all together as in my experience they are a huge waste of time.
They're too risk averse because they're investing their personal money, so they cling onto it like crazy, waiting until your company is a sure thing before they invest, but by then you'll have access to more VC investors than you can handle so why would you need angel investors then?
I would try to approach VCs instead as they're less risk averse and explain to them that you're growing quickly and need some funding to support your rising costs.
The sooner you get in contact with VCs the better since they'll be able to track your progress and when they see that you're continuing to grow, they will invest since they'll then trust that your company is headed in the right direction.
Also, see if you can raise some funding from friends and family. I know it's a hard thing to do to approach them since you don't want to risk losing their money and in some cases you don't want to come to them because you'd rather succeed without their help.
Swallow your pride and do it if that's what it takes. All that matters in the end is if you succeed; not how you did it.