I am sorry to hear that you have been dealing with bumps in the back of your throat and blisters on your tongue that have you worried. I am happy to give you some ideas about what might be going on, but ultimately I am going to recommend that you make an appointment with an ENT (Ear Nose Throat) physician to get evaluated. The reason for this is that they will be able to take more of history from you, and they will be able to perform a thorough exam which is ultimately what you need to get the most accurate answer. There are a number of different oral pathologies that can present with blisters, and depending on where exactly they are presenting, and whether there are other associated symptoms (such as blisters elsewhere in your body, such as on your skin) it can give a better idea about what might be going on. For instance, oral blisters can be from the herpes simplex virus. This is a virus that often lies dormant in the host until some sore of immunosuppression (such as being on steroids, or a high stress time in ones life) causes a flare up. An easy way to find out is to culture one of the blisters, which the ENT would be able to do.