A few comments:
a) No, nothing you described there seems to even be any sin, let alone mortal sin. Certainly not mortal sin.
b) It's early yet, since you've only just had your first confession, but it sounds like you have the anxiety of what is called scrupulosity.
Here is a description: newadvent.org/cathen/13640a.htm
If you find yourself constantly worrying that this or that was a sin, especially if you worry about mortal sins, then you should find a regular confessor and discuss such things with him.
Also, do you understand the requirements for mortal sin? Here is a description from the catechism:
1857 For a sin to be mortal, three conditions must together be met: "Mortal sin is sin whose object is grave matter and which is also committed with full knowledge and deliberate consent."131
1858 Grave matter is specified by the Ten Commandments, corresponding to the answer of Jesus to the rich young man: "Do not kill, Do not commit adultery, Do not steal, Do not bear false witness, Do not defraud, Honor your father and your mother."132 The gravity of sins is more or less great: murder is graver than theft. One must also take into account who is wronged: violence against parents is in itself graver than violence against a stranger.
1859 Mortal sin requires full knowledge and complete consent. It presupposes knowledge of the sinful character of the act, of its opposition to God's law. It also implies a consent sufficiently deliberate to be a personal choice. Feigned ignorance and hardness of heart133 do not diminish, but rather increase, the voluntary character of a sin.
Please note, mortal sin requires grave matter - it has to be something very serious. A small lie would not usually be considered grave matter, as you note in your first post.
Also note that you need knowledge (that whatever-it-is is wrong) and full consent. An unintentional lie cannot meet the requirement of full consent. You have to know that you're deliberately committing the sin at the time.
I hope this helps. All the best.