Medications even for a breastfeeding mom are useful. Zoloft for example has very little entry into the milk supply. Therapy and support groups are also helpful.
More likely is that you are swallowing air and these sharp pains are gas pains. Of course it would be wise to check with the internist to rule out any cardiac concerns.
I recommend treatment with SSRI medication and possible cognitive behavioral treatment along with a meditative practice to.have a tool to calm yourself.