My boyfriend goes soft during sex

There can be any number of reasons, including  the possibility that he feels pressured and this interferes with his performance; that pressure may be related to sexual performance or it may be worries about something totally unrelated.  Also, sometimes guys just go through periods where their erections are not as dependable; it can be a transient thing that comes and goes.  Another option: his penis has lost some of its sensitivity. Penile skin is very fragile, and when the penis experiences rough handling (no matter how pleasurable it may be), it can cause tiny layers of scar tissue. When these build up, they have a deadening effect on the penis, and that can interfere with the pleasurable sensation ns he experiences during sex.  His penis needs to be kept healthy and in good shape, so he should already be using a penis nutrient cream (health professionals recommend Man1 Man Oil), but he may not be. Suggest he use one, especially one with an ingredient (such as acetyl L carnitine) which is helpful in dealing with penis sensitivity. Hope things go well for you!