We started noticing dd1's sensory issues around 7yo, but in retrospect, they were there all along (like op said, from infancy) we just chalked them up to other things (her food allergies, her oral aversion, her GERD, her clumsiness was from Dad ). When we first went for an OT eval, the OT asked me about her infancy and when I described how she slept at daycare it suddenly hit me: she was the only kiddo who needed to be in a swing, with a receiving blanket horseshoe'd around her head, binky in, and a light blanket draped over the swing. What we just thought was quirkiness was actually SPD manifesting itself then. Her oral aversions are largely textural, but we thought it was because milk was in so many foods that we'd made her nervous about eating.
She was fairly adept at coping until she reached the developmental stage where kids are more self-conscious about behving differently. When you're 4-5yo everyone's a goofball, but at 7-8yo kids start wanting to act cool and her odd behaviors stood out more, e.g. putting her fingers in/over her ears when she was auditorally overstimulated and getting visibly distressed.
Have you ever read The Out of Sync Child? It's a great book about sensory issues, esp. in young childhood. HTH!