Getting second opinions is vital, even if you love and respect your primary doctor. Having a second set of eyes and a second brain look at your situation is always better.
If the second opinion is consistent with the first then you will feel more confident that you are heading in the correct direction. If it is different then it should make you stand up and take notice.
I have heard that sometimes people don't want to get a second opinion because they are concerned that the primary doctor will become insulted. This is very rare, oncologists expect and often appreciate hearing from another doctor. If your doctor isn't OK with a second opinion then they do not have enough confidence in their own work which tells me that you should move on to a different doctor.
Your goal is to do the best for yourself, not to make the doctor feel better about themselves.