"I attend church every week and every wed night but I do not attend Sunday school. Do I need to in need to be a true Christian?"
Hmm... I don't think God has an angel in heaven assigned to taking attendance in Church. Nor is it likely that he cares whether you are in service every time the doors are open. What does God ask of you?
Pretty simple actually. Remember in the Old Testament when God told Saul to wipe out everything in one of his battles? But Saul decided to allow his army to keep some of the bounty and then told the prophet that he intended it to be used as an "offering for the Lord". The prophet responded in a simple but profound way - "God desires obedience more than sacrifice."
Is God moving in your heart, telling you that you are not going to church enough? Do you feel his spirit moving you to be involved in a Sunday School class or Wednesday night service? If so, then you should probably obey the leading of the Lord or risk the consequences. Not a bolt of lighting, but a veil of separation from him.
God tells us what he wants in several ways 1. through scripture, 2. through prayer, through the fellowship of believers. There are probably others, but I will limit my time to these three:
1. Scripture - I am not talking about proof-texting here, or trying to find words that address your specific situation. Just this, God will not tell you to do anything that is in direct conflict with his word. for example, God will not tell you that it is OK to have an affair with another person's spouse. Sorry - that's outside the plan, no matter how much you may want to rationalize it.
2. Prayer - prayer and meditation are both crucial in the life of a Christian. When you pray and listen (meditate) you allow God to have the time and space necessary to speak to you. This may not come in an audible voice, but you can feel his presence move within you.
3. Fellowship - other believers can, and will, confirm the thoughts and visions that God gives to you. Of course, you will need to avail yourself of their wisdom my participating with them in community.
Want to be close to God (be a true Christian) - listen hard for his voice and then obey.