Hi there TakeControl, and welcome to Scarleteen.
You are correct that it takes a
lot of self-control and bodily control to use the withdrawal method properly, the difficulty you describe yourself having with this method is an experience many have, and you can read more about it on this page,
here. As you have already identified that you have pulled out late already a few times, are concerned that you may do so again, and want to minimize pregnancy risk (and also, I assume, STI risk), it is really important that you find another form of birth control that will work for you and your girlfriend going forward and do so before having sex again.
To answer your question about Plan B, which is a brand of the Emergency Contraceptive Pill, yes it can have some side effects. They are similar to what people might get on the combined pill, particularly when first starting and adjusting to it, like nausea, headaches, dizziness, breast tenderness and irregular or unexplained vaginal bleeding or spotting. This is also because it contains a bigger does of hormones than hormonal contraceptives designed to be taken regularly do. This is why it is
not meant to be used as an ongoing or sole contraceptive, and instead made to be used only for emergencies, and used infrequently. Not only is it much more expensive to use regularly as a form of contraception as compared to other kinds, it is also not as effective as other methods.
Have you and your girlfriend discussed some birth control options that could work for the both of you before? We have some great articles about this here that you could look at together, or read separately and discuss after; these kinds of conversations and choices are ones that should be discussed and made together:
It is also important to note that for protection from STIs, only
condoms can provide that. Also, the idea of vaginal "tightness" has a lot of misconceptions around it: as you also want your girlfriend to have a mutually enjoyable time, learning more about how the vagina can assist you with this:
A few choice words about "tightness".
I hope you find this information useful. There is a lot of what might be new info to you in here so please feel free to come back to this thread with any questions, clarifications, curiosities or concerns that you might want answered!