Missed periods and other health problems

My wife had her period last month around 13 th May. However, this month she did not have her period till date. From friday evening she was feeling a bit nausea and had a temperature of 100.4 throughout saturday. Temperature was back to normal from sunday after taking 1 Calpol. However, she is feeling a bit of nausea sometimes although there has been no vomiting. On saturday she also passed stool about 4 times. But after that it is only once on sunday. We are worried as she did not have her period yet. We always practise safe sex with condom only. Is this condition an indication of pregnancy. We are worried as we are not ready for children yet. Please suggest whether her condition is an indication of pregnancy. If so how we can confirm it and what can be done if we dont want a child now.