I think you are mistaking sensing for introverted sensing (Si). SJ and NP types use Si (SJ more than NP). Si compares now to the past. SP (This includes ISFPs) and NJ types use extroverted sensing (Se), meaning they like to live in the moment. SP types can still use Si, though. They just don't rely on it all the time.
Here's all the descriptions of the functions:
My MBTI Personality Type - Understanding MBTI Type Dynamics - The Eight Function-Attitudes
ISFP - Fi / Se / Ni / Te (Introverted Feeling / Extroverted Sensing / Introverted Intuition / Extroverted Thinking)
INFP - Fi / Ne / Si / Te (Introverted Feeling / Extroverted Intuition / Introverted Sensing / Extroverted Thinking)
I don't think that's a intuitive thing. Almost everyone I know (both sensing types and intuitive types) do that, including me. Hahaha. XD
You sound more like an ISFP to me, but there is a lot of arguments of the possibility of you being an INFP.
Here's a comparison of ISFP and INFP:
ISFP vs. INFP | Prelude Character Analysis
You should read these to a close friend or family member and ask which one sounds more like you, because sometimes it's easier for somebody else to have an idea of who you are than you to have an idea of who you are.
I hope I helped.