Shocked to find out I'm having twins

I went for my first appointment this week at 8 weeks 2 days and found out I was carrying twins. I was absolutely shocked, scared, nervous, and I panicked about our future. My husband and I have only ever wanted two children, and we already have a 4 year old boy. We live in a two bedroom house and have only my husband's income, as I've been a stay at home mom since our son was born. We know all babies are blessings, and we're excited to be parents again. But I'm having a hard time wrapping my head around being a mom of three in a two bedroom house with one income. My question is, if/ when will I stop feeling so panicked about having twins, and start being excited about having two babies to love plus my sweet boy I already have. Is it normal to feel this way? My husband is completely over the moon excited. He has no worries at all and can't wait for the twins to be here. I feel guilty feeling so panicked about it when he's so excited.