My septic tank appears to be overflowing out one of the inspection pipes.?

The toilets flush fine, we've only heard two gurgles, one out of each toilet, in the last 2 days. However, the cap of the inspection pipe has popped off and solid waste and toilet paper are overflowing into the yard. I know, very gross! However, the septic system has only been in use for one and a half years, and it was brand new when we moved here, when the house was built. We've had a lot, a TON of rain in the last week or so, and we're also a pretty big household (about 8 people give or take use the facilities on any given day) but we dont flush and wash down the drains anything that doesnt belong, and I dont use bleach or anything strong like that as cleaners. We've used RidX a few times, although from what Ive read that usually isnt even nessecary. Of course this happens on the a weekend, so it'll be Monday before we can even contact someone for help, so Im turning to you guys. Do we need to pump, or will the water eventually drain on its own naturally? Is this caused by a clog or blocked pipe somewhere, or is it just excessive water in the tank? Its not sludge coming up, its stuff straight from the toilets so I dont know if that means theres a clog somewhere, or theres just so much in the tank that its coming straight out instead of having anytime to settle. Please help! Any advice or guesses would be great. We're new homeowners and have never had to deal with a septic before and we're kinda losing it over this one. My husband is all ready to blame me because he seems to think flushing toilet paper is what caused the whole mess, but Im pretty sure toilet paper gets taken care of by the chemicals in the tank and doesnt actually harm anything :( Please help!