BBT appropriate thermometer?

So, DH and I miscarried our first in May at 13 weeks. We're now ready to TTC again. I've already O'd and BD'd each day of my window. 
If we don't conceive this cycle I'm going to track my BBT. I was just wondering though, the thermometer we have in the house is a Vicks v900r. The manual says it's accurate to +/- .2 degrees. Is this accurate enough?
I'm not interested in spending a fortune on conception quite yet. We weren't trying (though not preventing) when we first got pregnant and my cycles are freaky regular (as in I *knew* when my period was hours late) and I can feel when I ovulate, etc so my hope is it will happen naturally fairly soon. But if not then I will get a more appropriate/accurate thermometer.
Also, do I have to take it rectally? Or can I temp in my mouth?