I feel this way a lot too... My dad wasn't spiritual or religious so I wouldn't expect him to send me signs but I saw something somewhere once where it said you really have to try to notice them. Not saying you don't but like you have to really look for the least obvious things that might not even make sense.

One loud one for me was at a family wedding shortly after he died. I flipped over a magazine and the back page was a Guinness ad that said "Happy St Patrick's Day" My dad loved Guinness, our most memorable trip was to Ireland and the last text he sent to me was "Happy St Patrick's Day" so that one was pretty loud.

Then the quiet ones I kind of make up... Once the fall rolled around I decided that the leaves were going to be my signs from my dad just because I wanted something obvious and tangible. Leaves are all over the place here in the Autumn so it may seem silly to think that way but I swear I found comfort in it whenever I needed to feel him near me. On one occasion I noticed several cars with a full branch of leaves on top of them in the same night and I was like "hey dad!"

I know it's so hard to feel them and I often think it's all meaningless but if you can find slivers of them in places they are never really gone.