Should I Trust a Digital Thermometer?

I feel a little ill (it's end of flu season here, but I probably have just some light cold) so I measured my body temperature (in armpit). Thrice. With these values:

1. 35.8 °C,
2. 35.9 °C,
3. 35.7 °C.

Should I trust that? Especially if my colleague has measured himself a normal body temperature of 36.7 °C. I wonder if I just put the thermometer wrongly in the armpit or if it's measuring incorrectly… I wish I had a good old mercurial thermometer to check…