To sum it up:
- You have cramps
- You have achy legs (not a typical pregnancy sign, but could be)
- You have frequent urination, definitely a pregnancy sign
- You have missed your period by four days!!!
You have pretty convincing early pregnancy symptoms.
You can take a pregnancy test from the first day on which your period was supposed to come, but didn't, so on the very day of your missed period. It's not too early to take a test! I hope you want to be pregnant because it sounds like you very well could be, but only a pregnancy test will tell you for sure!