Problems with erections. With me?

Hey there , a year ago I got involved in sexual activity & it was going all good we were indulged in foreplay & during that moment she drafted her hands on my erect penis and started stroking it ,as it was 1st time for me that a girl was holding my penis I ejaculated , Again we got into foreplay after some time I rushed for sexual intercourse as my penis was again erected the moment I put a condom the stiffness went away a little but still I went for intercourse and was not able to find the vaginal opening i.e where I have to exactly put it, so she extended her hand to guide my penis and again from her touch I ejaculated but that was embarrassing for me as I wasn't able to do it later on I ended up not having sex  The same thing happened to me few months later but during those months in between I was obversing my erections it's been a year I am doing that, lately I was again with a girl and I was not able to have sex coz of semi erect penis what is the problem with me? i took tazzle 10