Can a person do things against their own will and be conscious of it at the same time?
Can a person do things they know they are not willing to do?
This is a little tricky to answer without parsing it as follows: can someone's earnestly stated desires be different to the desires implied by their actions?
Phrasing your question this way is important because what someone wants is unknowable: people could be lying to themselves, or lying to us, or simply lacking the insight to fully understand the motivations underpinning their behaviour. The intent behind a behaviour is even more unknowable: it can only be inferred from observation. Thus, although we presume that a dog eats because its hungry, and drinks water because it's thirsty, we need to be careful in recognising that while this is certainly a reasonable inference, nonetheless it is still only an inference.
I am sure you will also find some very rare syndrome that is sexier e.g. alien claw hand or similar, but conceptually I would suggest drug addiction is the best example of this.
Although not immediately apparent, the phenomenology of the drug-taking behaviour is very reminiscent of what you're describing. The two core features of addiction are craving and compulsion -- the latter is of relevance to your question. At its core, compulsive drug-taking behaviour is a decoupling of an earnestly stated (or believed) desire and action that suggests something entirely to the contrary.
I am a firm believer of the principle of free-will, but wanted to see if there was any examples(or case examples) of people knowingly doing things against their own will.
Typically, drug addicts will consciously state that they do not want to consume drugs, but that they are lead to do so by some uncontrollable compulsion. That is, they continue to consume drugs despite the clear acknowledgement that it is no longer in their interests to do so and conveying an earnest desire to not consume drugs.
I know that we can be pressured to do things and make hard choices, but the choice is still that of the individual.
The concept of drug addiction creates problems for proponents of free will: if addiction is a choice, then so are the harms. The moral culpability of the addict came be framed in either two ways:
Deviancy. The drug addict values the wrong things. They belong in prison.
Weakness. The drug addict has the same values as us, but is too weak-willed to pursue/obtain/keep them. In recognising their weakness, they deserve help.
Generally, to reconcile the concept of addiction as choice (free will) versus addiction as disease (addiction) those in the literature will attempt to describe the initial use of drugs as a volitional act, but one which becomes less and less freely chosen over time. The adaptive changes that are observed in the brain with repetitive drug administration i.e. addiction support are generally used to argue this point.