Thal babies can be very susceptible to infection the first few months so fevers need to be paid attention to. The doctor has given you a temperature to watch for. Low grade fevers are common but if it gets above this, you should get her in and have it checked. This is a precaution and doesn't mean anything serious is wrong, but it is often easier to control an infection if it is attended to promptly, and with thals, infections can get out of hand if not attended to, so the doctor has given you this instruction.
The fussiness that Lauryn is showing is common in babies, especially when they have switched to formula. If it persists, you may need to try a different formula, and of course, the formula should always be iron free.
Chrissy, I would just like to say how good it is to see how much strength you've found since first learning your child might be thal. I know that initially it was a great shock and it is so much to deal with, but I think you've shown that you're gonna be a great mom.