Stay home if you can afford it, you'll never get back these years so it is well worth it. I stayed home for the first 18 mths, then went back to work. It is much harder to spend quality time with your children, meet the demands of daily living (cooking, cleaning, laundry etc) and have a happy marriage when you work outside the home. I am far more tired and grumpy now then I ever was as a full time mom.
As far as being frustrated, try doing some things with other moms w/ kids. I always enjoyed playgroups as much as my kids did. I chatted with the adults while my kids were off playing. Even though I was still with them, it was almost like having time off.
Speaking of time off, try hiring a babysitter every once in a while just to give yourself a break. Even a few hours every few weeks can make you feel refreshed. You can use this time to go out to lunch, walk around Wal-Mart or deep clean your kitchen. What ever makes you feel good.
Finally be sure to split time with your husband for things like putting them to bed. You could alternate nights or just have him do it every 3rd night; as long as you aren't doing it all the time. Also ask him to take the kids out for a few hours on the weekend. Use this time to read a book, take a nap, whatever.
The point is whether you are working outside the home or inside, you are still working and need time off too. AS I explained to my husband: I am a better mother and wife when I get some time off. In my house my husband gets some "time off" on Saturday and I get some on Sunday afternoon. This way everybody is happy. Good luck to you.