Anyone have advice?

Looking to hear some perspectives. My son has refused the breast for about a month and a half now so I've been pumping and offering mainly formula. I already had an under supply so I've been combo feeding since around 3 months. I was only able to pump about 2 ounces 3-4 times a day. Now since a recent trip away for a wedding, during which I was insanely busy, my supply has dropped again. I get about an ounce 2x a day. I'm just wondering.. do I throw in the towel at the 5 month mark or do I pump like crazy to get my supply back? I'm just so tired of it but I feel soo guilty for not trying harder.