1stTime, how exciting for you to go to Italy. It will be the first of many European visits I'm sure. I'm going to Italy next September for the second time, third for Venice which I love. I've done carry-on each time, learning and improving each trip. I've been able to cut weight and struggling less with practice. There are sample packing lists in Travel Tips and on the forum (use the search feature).
For an example, here's what I'm taking next year for 25 days, which is just about the same as I took this year to Germany/Austria for 29 days. The list includes what I wear on the plane.
3 pair pants (I wear leggings because they pack small)
7 shirts/tunics, long and short sleeve
5 sets underwear
1 set PJs
2 pair shoes, walking shoes and sandals
1 lightweight jacket
1 packable rain poncho
I don't know how old you are, but as I age, I take more "get me through the day" supplies, eg drugs, supplements, misc needs. These all add weight so only take the bare essentials. Electronics add weight too. So do lotions and potions.
As you attempt to pack lighter and smaller, first check your airlines' size and weight requirements; that's your maximum packing goal. Then make a detailed packing list. Test pack, revamp list, weigh what you're taking, test pack again, repeat until you are happy with your list. Packing cubes are very helpful to keep things organized. Remember that only you will know what you wore each day. No one will nor will they care.
Here's a concurrent thread about laundry that may help you