It may be hard to wait, especially since you really want this, but I would suggest it. I have wasted so much money and time thinking that I was pregnant and if I would have been patient and just waited a touch longer, I wouldn't have. It is always possible that you are pregnant, but those are also symptoms I experience when I am about to start my cycle.
If you have the extra time and money, there is no harm in calling and getting an appointment though. Whatever helps give you peace of mind is what I would do. You have two other children to care for and if your mind is at peace, it will be better for all three (possibly four) of you. I know that from experience! ^_^