Kinda worried. My premie baby is 3.5 months old. I opted for no birth control since we want another…

Kinda worried. My premie baby is 3.5 months old. I opted for no birth control since we want another and want to keep them close in age. But we had such a hard time getting pregnant and both of us have fertility issues. So not worried about getting pregnant too early. But I’m nauseous, hot, super thirsty I already drink about a gallon a day I’m more thirsty than that, getting car sick, been having tummy upset. Wondering if I’m pregnant again so soon. I have about 2 months of breast milk frozen but I want my son on breast milk for a yr at least. So worried if I’m pregnant I will loose my milk. Anyone have experience breast feeding while pregnant? I make between 1100-1400 ml a day.